Online Etymology Dictionary

understand (v.): Old English understandan "comprehend, grasp the idea of," probably literally "stand in the midst of," from under + standan "to stand" (see stand (v.)). If this is the meaning, the under is not the usual word meaning "beneath," but from Old English under, from PIE *nter- "between, among" (source also of Sanskrit antar "among, between," Latin inter "between, among," Greek entera "intestines;" see inter-). Related: Understood; understanding.

That is the suggestion in Barnhart, but other sources regard the "among, between, before, in the presence of" sense of Old English prefix and preposition under as other meanings of the same word. "Among" seems to be the sense in many Old English compounds that resemble understand, such as underniman "to receive," undersecan "examine, investigate, scrutinize" (literally "underseek"), underðencan "consider, change one's mind," underginnan "to begin." It also seems to be the sense still in expressions such as under such circumstances.

Perhaps the ultimate sense is "be close to;" compare Greek epistamai "I know how, I know," literally "I stand upon." Similar formations are found in Old Frisian (understonda), Middle Danish (understande), while other Germanic languages use compounds meaning "stand before" (German verstehen, represented in Old English by forstanden "understand," also "oppose, withstand"). For this concept, most Indo-European languages use figurative extensions of compounds that literally mean "put together," or "separate," or "take, grasp" (see comprehend). Old English oferstandan, Middle English overstonden, literally "over-stand" seem to have been used only in literal senses. For "to stand under" in a physical sense, Old English had undergestandan.
understanding (n.): Old English understanding "comprehension," verbal noun from understand (v.). Meaning "mutual agreement" is attested from 1803.
understandable (adj.): late 14c., "able to understand;" late 15c., "able to be understood," from understand + -able. Related: Understandably.
under (prep., adv.): Old English under (prep.) "beneath, among, before, in the presence of, in subjection to, under the rule of, by means of," also, as an adverb, "beneath, below, underneath," expressing position with reference to that which is above, from Proto-Germanic *under- (source also of Old Frisian under, Dutch onder, Old High German untar, German unter, Old Norse undir, Gothic undar), from PIE *ndher- "under" (source also of Sanskrit adhah "below;" Avestan athara- "lower;" Latin infernus "lower," infra "below").

Productive as a prefix in Old English, as in German and Scandinavian (often forming words modeled on Latin ones in sub-). Notion of "inferior in rank, position, etc." was present in Old English. With reference to standards, "less than in age, price, value," etc., late 14c. As an adjective, "lower in position; lower in rank or degree" from 13c. Also used in Old English as a preposition meaning "between, among," as still in under these circumstances, etc. (though this may be an entirely separate root; see understand).

Under the weather "indisposed" is from 1810. Under the table is from 1921 in the sense of "very drunk," 1940s in sense of "illegal." To get something under (one's) belt is from 1954; to keep something under (one's) hat "secret" is from 1885; to have something under (one's) nose "in plain sight" is from 1540s; to speak under (one's) breath "in a low voice" is attested from 1832. To be under (someone's) thumb "entirely controlled" (by that person) is recorded from 1754.
misunderstand (v.): c. 1200; see mis- (1) + understand. Related: Misunderstood; misunderstanding.
undertake (v.): c. 1200, "to entrap;" c. 1300, "to set about (to do)," from under + take (v.). Similar formation in French entreprendre "to undertake," from entre "between, among" + prendre "to take." The under in this word may be the same one that also may form the first element of understand. Old English had underniman "to trap, accept" (cognate with Dutch ondernemen, German unternehmen).
capiche: 1940s slang, from Italian capisci? "do you understand?" from capire "to understand," from Latin capere "seize, grasp, take" (see capable). Also spelled coppish, kabish, capeesh, etc.
make out (v.): c. 1600, "get along," from make (v.) + out (adv.). Sense of "understand" is from 1640s; sexual sense first recorded 1939.
interpretable (adj.): 1610s, from Late Latin interpretabilis "that can be explained or translated," from Latin interpretari "explain, expound, understand" (see interpret).
intelligible (adj.): late 14c., "able to understand, intelligent," from Latin intelligibilis, intellegibilis "that can understand; that can be understood," from intellegere "to understand, come to know" (see intelligence). In Middle English also "to be grasped by the intellect" (rather than the senses). In English, sense of "capable of being understood, that can be understood" first recorded c. 1600. Related: Intelligibly.
Abderian laughter (n.): from Abdera, in Thrace, whose citizens were proverbial as rustic simpletons who would laugh at anything or anyone they didn't understand (making their town the Hellenic equivalent of Gotham).
realize (v.): 1610s, "bring into existence," from French réaliser "make real" (16c.), from Middle French real "actual" (see real (adj.)). Sense of "understand clearly, make real in the mind" is first recorded 1775. Sense of "obtain, amass" is from 1753. Related: Realized; realizing.
grok (v.): "to understand empathically," 1961, arbitrary formation by U.S. science fiction writer Robert A. Heinlein (1907-1988) in his book "Stranger in a Strange Land." In popular use 1960s; perhaps obsolete now except in internet technology circles.
unclear (adj.): c. 1300, "not easy to understand," from un- (1) "not" + clear (adj.). Similar formation in Middle Dutch onclaer, Dutch onklaar, German unklar, Old Norse uklarr, Danish uklar, Swedish oklar. Of persons, in sense of "uncertain, doubtful," it is recorded from 1670s.
fathom (v.): Old English fæðmian "to embrace, surround, envelop," from a Proto-Germanic verb derived from the source of fathom (n.); cognates: Old High German fademon, Old Norse faþma. The meaning "take soundings" is from c. 1600; its figurative sense of "get to the bottom of, penetrate with the mind, understand" is from 1620s. Related: Fathomed; fathoming.
interpretative (adj.): "meant to explain," 1560s, from past participle stem of Latin interpretari "explain, expound; understand" (see interpret). Interpretive means the same but is considered to be less correctly formed, because -ive adjectives are normally formed on the Latin past participle. Related: Interpretatively.
insense (v.): "teach, instruct, cause (someone) to understand," c. 1400, ensense, from Old French ensenser "to enlighten, to bring to sense," from en- "in" (see in- (2)) + sens (see sense (n.)). "From 17th c. app. only dialectal (chiefly northern), or in writers under dialectal influence" [OED].
distinctly (adv.): late 14c., from distinct + -ly (2).
[D]istinctly, in the sense really quite, is the badge of the superior person indulgently recognizing unexpected merit in something that we are to understand is not quite worthy of his notice. [Fowler]
skilled (adj.): 1550s, past participle adjective from skill (v.) "to have personal and practical knowledge" (c. 1200), from Old Norse skilja "separate, part, divide; break off, break up; part company, take leave; discern, distinguish; understand, find out; decide, settle," from the source of skill (n.).
intellection (n.): c. 1400, intellecioun "meaning, purpose;" mid-15c., "the understanding;" 1610s, "an act of understanding," from Old French intelleccion and directly from Medieval Latin intellectionem (nominative intellectio), noun of action from past participle stem of Latin intelligere "to understand, discern" (see intelligence).
spiritual (adj.): c. 1300, "of or concerning the spirit" (especially in religious aspects), from Old French spirituel, esperituel (12c.) or directly from a Medieval Latin ecclesiastical use of Latin spiritualis "of or pertaining to breath, breathing, wind, or air; pertaining to spirit," from spiritus "of breathing, of the spirit" (see spirit (n.)). Meaning "of or concerning the church" is attested from mid-14c. Related: Spiritually. An Old English word for "spiritual" was godcundlic.
In avibus intellige studia spiritualia, in animalibus exercitia corporalia [Richard of St. Victoror (1110-1173): "Watch birds to understand how spiritual things move, animals to understand physical motion." - E.P.]
acknowledge (v.): 1550s, a blend of Middle English aknow (from Old English oncnawan "understand," from on + cnawan "recognize;" see know) and Middle English knowlechen "admit, acknowledge" (c. 1200; see knowledge). In the merger, a parasitic -c- slipped in, so that while the kn- became a simple "n" sound (as in know), the -c- stepped up to preserve, in this word, the ancient "kn-" sound. Related: Acknowledged; acknowledging.
intellect (n.): "the sum of the cognitive facilities (except sense or sense and imagination), the capacity for reasoning truth," late 14c. (but little used before 16c.), from Old French intellect "intellectual capacity" (13c.), and directly from Latin intellectus "discernment, a perception, understanding," noun use of past participle of intelligere "to understand, discern" (see intelligence). The Latin word was used to translate Greek nous "mind, thought, intellect" in Aristotle.
interpret (v.): late 14c., "expound the meaning of, render clear or explicit," from Old French interpreter "explain; translate" (13c.) and directly from Latin interpretari "explain, expound, understand," from interpres "agent, translator," from inter- "between" (see inter-) + second element of uncertain origin, perhaps related to Sanskrit prath- "to spread abroad," PIE *per- (5) "to traffic in, sell" (see pornography). Related: Interpreted; interpreting.
epistemology (n.): "theory of knowledge," 1856, coined by Scottish philosopher James F. Ferrier (1808-1864) from Greek episteme "knowledge, acquaintance with (something), skill, experience," from Ionic Greek epistasthai "know how to do, understand," literally "overstand," from epi "over, near" (see epi-) + histasthai "to stand," from PIE *sta- "to stand" (see stet). The scientific (as opposed to philosophical) study of the roots and paths of knowledge is epistemics (1969). Related: Epistemological; epistemologically.
double entendre: also double-entendre, 1670s, from French (where it was rare and is now obsolete), literally "a twofold meaning," from entendre (now entente) "to hear, to understand, to mean," from Latin intendere (see intend). The proper Modern French phrase would be double entente, but the phrase has become established in English in its old form.
message (n.): c. 1300, "communication transmitted via a messenger," from Old French message "message, news, tidings, embassy" (11c.), from Medieval Latin missaticum, from Latin missus "a sending away, sending, despatching; a throwing, hurling," noun use of past participle of mittere "to send" (see mission). The Latin word is glossed in Old English by ærende. Specific religious sense of "divinely inspired communication via a prophet" (1540s) led to transferred sense of "the broad meaning (of something)," first attested 1828. To get the message "understand" is from 1960.
comprehend (v.): mid-14c., "to understand," from Latin comprehendere "to take together, to unite; include; seize" (of catching fire or the arrest of criminals); also "to comprehend, perceive" (to seize or take in the mind), from com- "completely" (see com-) + prehendere "to catch hold of, seize" (see prehensile). Related: Comprehended; comprehending. Compare sense development in German begriefen, literally "to seize," but, through the writings of the 14c. mystics, "to seize with the mind, to comprehend."
savvy (n.): 1785, "practical sense, intelligence;" also a verb, "to know, to understand;" West Indies pidgin borrowing of French savez(-vous)? "do you know?" or Spanish sabe (usted) "you know," both from Vulgar Latin *sapere, from Latin sapere "be wise, be knowing" (see sapient). The adjective is first recorded 1905, from the noun. Related: Savvily; savviness.
skill (n.): late 12c., "power of discernment," from Old Norse skil "distinction, ability to make out, discernment, adjustment," related to skilja (v.) "to separate; discern, understand," from Proto-Germanic *skaljo- "divide, separate" (source also of Swedish skäl "reason," Danish skjel "a separation, boundary, limit," Middle Low German schillen "to differ," Middle Low German, Middle Dutch schele "separation, discrimination;" see shell (n.)). Sense of "ability, cleverness" first recorded early 13c.
selfish (adj.): 1630s, from self- + -ish. Said in Hacket's life of Archbishop Williams (1693) to have been coined by Presbyterians. In the 17c., synonyms included self-seeking (1620s), self-ended and self-ful.
Let us understand what our own selfish genes are up to, because we may then at least have the chance to upset their designs. [Richard Dawkins, "The Selfish Gene," 1976]
Related: Selfishly; selfishness. Similar formations in German selbstisch, Swedish sjelfvisk, Danish selvisk.
intellectual (adj.): late 14c., "grasped by the understanding" (rather than by the senses), from Old French intellectuel (13c.) and directly from Latin intellectualis "relating to the understanding," from intellectus "discernment, understanding," noun use of past participle of intelligere "to understand, discern" (see intelligence).

Sense of "characterized by a high degree of intellect" is from 1819. Meaning "appealing to or engaging the mental powers" is from 1834. Intellectual property "products of the intellect" is attested from 1845. Adjective formations in the sense "of or pertaining to the intellect" included intellective (early 15c.), intellectile (1670s).
interpretation (n.): mid-14c. "a translated text, a translation" (late 13c. in Anglo-French), from Old French interpretacion, entrepretatiun "explanation, translation" (12c.) and directly from Latin interpretationem (nominative interpretatio) "explanation, exposition," noun of action from past participle stem of interpretari "explain, expound; understand" (see interpret).

From late 14c. as "act or process of explaining or interpreting; an explanation; construction placed upon an action." Meaning "dramatic or musical representation" is from 1880.
cheese (v.): "stop (what one is doing), run off," 1812, thieves' slang, of uncertain origin. Meaning "to smile" is from 1930 (see cheese (n.1)). For meaning "to annoy," see cheesed.
CHEESE IT. Be silent, be quiet, don't do it. Cheese it, the coves are fly; be silent, the people understand our discourse. ["Dictionary of Buckish Slang, University Wit, and Pickpocket Eloquence," London, 1811]
linkage (n.): "system of combined links," 1874, originally in mechanical engineering, from link (v.) + -age.
To understand the principle of Peaucellier's link-work, it is convenient to consider previously certain properties of a linkage, (to coin a new and useful word of general application), consisting of an arrangement of six links, obtained in the following manner ... (etc.). ["Recent Discoveries in Mechanical Conservation of Motion," in "Van Nostrand's Eclectic Engineering Magazine," vol. XI, July-December 1874]
ken (v.): "to know, understand, take cognizance of," a word surviving mainly in Scottish and northern England dialect, from Middle English kennen, "make known; give instruction to; be aware, know, have knowledge of, know how to; recognize by sight; see, catch sight of," a very common verb, from Old English cennan "make known, declare, acknowledge" (in late Old English also "to know"), originally "cause to know, make to know," causative of cunnan "to become acquainted with, to know" (see can (v.)). Cognate with German kennen, Danish kjende, Swedish känna. Related: Kenned; kenning.
dig (v.): early 14c. (diggen), of uncertain origin, perhaps related to dike and ditch, either via Old French diguer (ultimately from a Germanic source), or directly from an unrecorded Old English word. Native words were deolfan (see delve), grafan (see grave (v.)).

Slang sense of "understand" first recorded 1934 in African-American vernacular, probably based on the notion of "excavate." A slightly varied sense of "appreciate" emerged 1939. Strong past participle dug appeared 16c., but is not etymological. Related: Digging.
wit (v.): "to know" (archaic), Old English witan (past tense wast, past participle witen) "to know, beware of or conscious of, understand, observe, ascertain, learn," from Proto-Germanic *witan "to have seen," hence "to know" (source also of Old Saxon witan, Old Norse vita, Old Frisian wita, Middle Dutch, Dutch weten, Old High German wizzan, German wissen, Gothic witan "to know"), from PIE *weid- (see wit (n.)). The phrase to wit, almost the only surviving use of the verb, is first recorded 1570s, from earlier that is to wit (mid-14c.), probably a loan-translation of Anglo-French cestasavoir, used to render Latin videlicet (see viz.).
fort (n.): mid-15c., "fortified place, stronghold," from Old French fort "fort, fortress; strong man," noun use of adjective meaning "strong, stout, sturdy; hard, severe, difficult; hard to understand; dreadful, terrible; fortified" (10c.), from Latin fortis "strong, mighty; firm, steadfast; brave, spirited," from Old Latin forctus, possibly from PIE root *bhergh- (2) "high, elevated," with derivatives referring to hills and hill-forts (see barrow (n.2)). Or possibly from *dher- (2) "to hold firmly, support." Figurative use of hold the fort attested from 1590s.
perceive (v.): c. 1300, via Anglo-French parceif, Old North French *perceivre (Old French perçoivre) "perceive, notice, see; recognize, understand," from Latin percipere "obtain, gather, seize entirely, take possession of," also, figuratively, "to grasp with the mind, learn, comprehend," literally "to take entirely," from per "thoroughly" (see per) + capere "to grasp, take" (see capable).

Replaced Old English ongietan. Both the Latin senses were in Old French, though the primary sense of Modern French percevoir is literal, "to receive, collect" (rents, taxes, etc.), while English uses the word almost always in the metaphorical sense. Related: Perceived; perceiving.
lucid (adj.): 1590s, "bright, shining," from Latin lucidus "light, bright, clear," figuratively "perspicuous, lucid, clear," from lucere "to shine," from lux (genitive lucis) "light," from PIE root *leuk- "to shine, be bright" (see light (n.)). Sense of "easy to understand" first recorded 1786. Lucid interval "period of calm or temporary sanity" (1580s) is from Medieval Latin lucida intervalla (plural), which was common in medieval English legal documents (non est compos mentis, sed gaudet lucidis intervallis). Related: Lucidly; lucidness (1640s).
hemorrhage (v.): by 1882, from hemorrhage (n.). Related: Hemorrhaged; hemorrhaging.
Slang in Reports: B.I.D. for "Brought in Dead" and "Dotty" are, [Mr. Sidney Holland of London Hospital] considers, permissible expressions, but he draws the line at "fitting" and "hæmorrhaging." Only such terms, he says, should be used as outside doctors will understand. We would say that on a point of such odiously bad taste he might have been much more severe. [Lavinia L. Dock, "The American Journal of Nursing," 1906]
know (v.): Old English cnawan (class VII strong verb; past tense cneow, past participle cnawen), "perceive a thing to be identical with another," also "be able to distinguish" generally (tocnawan); "perceive or understand as a fact or truth" (opposed to believe); "know how (to do something)," from Proto-Germanic *knew- (source also of Old High German bi-chnaan, ir-chnaan "to know").

This is from PIE root *gno- "to know" (source also of Old Persian xšnasatiy "he shall know;" Old Church Slavonic znati, Russian znat "to know;" Latin gnoscere; Greek *gno-, as in gignoskein; Sanskrit jna- "know").

For pronunciation, see kn-. Once widespread in Germanic, the verb is now retained there only in English, where it has widespread application, covering meanings that require two or more verbs in other languages (such as German wissen, kennen, erkennen and in part können; French connaître "perceive, understand, recognize," savoir "have a knowledge of, know how;" Latin scire "to understand, perceive," cognoscere "get to know, recognize;" Old Church Slavonic znaja, vemi). The Anglo-Saxons also used two distinct words for this, the other being witan (see wit (v.)).

From c. 1200 as "to experience, live through." Meaning "to have sexual intercourse with," also found in other modern languages, is attested from c. 1200, from the Old Testament (Gen. iv.1). Attested from 1540s in colloquial phrases suggesting cunning or savvy (but often in the negative); to not know one's ass from one's elbow is from 1930.

As far as (one) knows "to the best of (one's) knowledge" is late 14c. Expression God knows is from c. 1400. To know too much (to be allowed to live, escape, etc.) is from 1872. To know better "to have learned from experience" is from 1704.

You know as a parenthetical filler is from 1712, but it has roots in 14c. You know as a euphemism for a thing or situation unmentionable is from 1867; you-know-who for a person it is thought best not to name (but implying the hearer knows) is from 1840.

As an expression of surprise, what do you know attested by 1914. Don't I know it in the opposite sense ("you need not tell me") is from 1874. You never know as a response to something unexpected is attested from 1924.
critic (n.): 1580s, "one who passes judgment," from Middle French critique (14c.), from Latin criticus "a judge, literary critic," from Greek kritikos "able to make judgments," from krinein "to separate, decide" (see crisis). Meaning "one who judges merits of books, plays, etc." is from c. 1600. The English word always had overtones of "censurer, faultfinder."
To understand how the artist felt, however, is not criticism; criticism is an investigation of what the work is good for. ... Criticism ... is a serious and public function; it shows the race assimilating the individual, dividing the immortal from the mortal part of a soul. [George Santayana, "The Life of Reason," 1906]

A perfect judge will read each work of wit
With the same spirit that its author writ;
[Pope, "An Essay on Criticism," 1709]
intelligence (n.): late 14c., "the highest faculty of the mind, capacity for comprehending general truths;" c. 1400, "faculty of understanding, comprehension," from Old French intelligence (12c.) and directly from Latin intelligentia, intellegentia "understanding, knowledge, power of discerning; art, skill, taste," from intelligentem (nominative intelligens) "discerning, appreciative," present participle of intelligere "to understand, comprehend, come to know," from inter- "between" (see inter-) + legere "choose, pick out, read" (see lecture (n.)).

Meaning "superior understanding, sagacity, quality of being intelligent" is from early 15c. Sense of "information received or imparted, news" first recorded mid-15c., especially "secret information from spies" (1580s). Meaning "a being endowed with understanding or intelligence" is late 14c. Intelligence quotient first recorded 1921 (see I.Q.).
bop (n.): 1948, shortening of bebop or rebop; as a verb, "play bop music, play (a song) in a bop style," from 1948. It soon came to mean "do any sort of dance to pop music" (1956). Related: Bopped; bopping.

The musical movement had its own lingo, which was in vogue in U.S. early 1950s. "Life" magazine [Sept. 29, 1952] listed examples of bop talk: crazy "new, wonderful, wildly exciting;" gone (adj.) "the tops--superlative of crazy;" cool (adj.) "tasty, pretty;" goof "to blow a wrong note or make a mistake;" hipster "modern version of hepcat;" dig "to understand, appreciate the subtleties of;" stoned "drunk, captivated, ecstatic, sent out of this world;" flip (v.) "to react enthusiastically." [Life Sept. 29, 1952]
truck (n.1): "vehicle," 1610s, originally "small wheel" (especially one on which the carriages of a ship's guns were mounted), probably from Latin trochus "iron hoop," from Greek trokhos "wheel," from trekhein "to run" (see truckle (n.)). Sense extended to "cart for carrying heavy loads" (1774), then in American English to "motor vehicle for carrying heavy loads" (1913), a shortened form of motor truck in this sense (1901).
There have also been lost to the enemy 6,200 guns, 2,550 tanks and 70,000 trucks, which is the American name for lorries, and which, I understand, has been adopted by the combined staffs in North-West Africa in exchange for the use of the word petrol in place of gasolene. [Winston Churchill, address to joint session of U.S. Congress, May 19, 1943]
Truck stop is attested from 1956.
bisexual (adj.): 1824, "having both sexes in one being, hermaphroditic," from bi- + sexual. Meaning "attracted to both sexes" is from 1914; the noun in this sense is attested from 1922, and compare bisexuality. Not in general use until 1950s. Ambisexual was proposed in this sense early 20c.
I suggest that the term ambisexuality be used in psychology instead of the expression "bisexual predisposition." This would connote that we understand by this predisposition, not the presence of male and female material in the organism (Fliess), nor of male and female sex hunger in the mind, but the child's psychical capacity for bestowing his erotism, originally objectless, on either the male or the female sex, or on both. [S. Ferenczi, "Sex in Psycho-Analysis," transl. Ernest Jones, Boston, 1916]
stroppy (adj.): "rebellious," by 1943, British nautical slang, perhaps a slang mangling of obstreperous. "Sea Passages: A Naval Anthology and Introduction to the Study of English" [1943, Geoffrey Callender] quotes from a letter:
Why Nobby should reckon that his raggie should blow the gaff, when there are crushers everywhere, leaves me guessing; but there it is. In the last dog he rounded on me and called me a white rat. I got stroppy and told him he was shooting a line: but all he said was, 'Oh! choke your luff! I'm looking for another oppo you snivelling sand-catcher.' So that looks like paying off.
to which Callender adds, "There is nothing in this letter which an active service rating could fail to understand."
jolie laide (n.): "girl or woman whose attractiveness defies standards of beauty," 1849, a French expression (by 1780 in French), from fem. singular of joli "pretty" (see jolly) + laid "ugly," from Frankish *laid (see loath (adj.)).
Of beauty, as we narrowly understand it in England, [the 18c. French woman of society] had but little; but she possessed so many other witcheries that her habitual want of features and complexion ceased to count against her. Expression redeemed the absence of prettiness and the designation jolie laide was invented for her in order to express her power of pleasing despite her ugliness. ["The Decadence of French Women," Blackwood's Edinburgh Magazine, October 1881]