Online Etymology Dictionary

know (n.): "inside information," 1883, in in the know, from know (v.) Earlier it meant "knowledge, fact of knowing" (1590s).
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.
know-nothing (n.): 1827, "ignoramus," from know (v.) + nothing. As a U.S. nativist political party, active 1853-56, the name refers to the secret society at the core of the party, about which members were instructed to answer, if asked about it, that they "know nothing." The party eventually merged into the Republican Party. Related: Know-nothingism.
know-how (n.): also knowhow, "technical expertise," 1838, American English, from know (v.) + how (adv.).
know-it-all (n.): "one deemed (over)full of information or correct answers," 1895, from verbal phrase; see know (v.). Earlier in the same sense was know-all (1862); and Mr. Know-All was a minor character in Bunyan's "The Holy War" (1682).
knowing (adj.): "with knowledge of truth," late 14c., present participle adjective from know (v.). From c. 1500 as "shrewd, sharp, smart." Related: Knowingly.
known (adj.): mid-13c., knouen, "well-known, famous, notorious," past participle adjective from know (v.). From early 14c. as "recognized, not secret; familiar, not strange." As a noun, "that which is known," by 1863; earlier "famous person" (1835). In Middle English it meant "one's acquaintances." To make (something) known is from mid-14c.
knowable (adj.): c. 1400, from know (v.) + -able.
well-known (adj.): late 15c., from well (adv.) + past participle of know (v.).
knowledge (n.): early 12c., cnawlece "acknowledgment of a superior, honor, worship;" for first element see know (v.). The second element is obscure, perhaps from Scandinavian and cognate with the -lock "action, process," found in wedlock.

From late 14c. as "capacity for knowing, understanding; familiarity;" also "fact or condition of knowing, awareness of a fact;" also "news, notice, information; learning; organized body of facts or teachings." Sense of "sexual intercourse" is from c. 1400. Middle English also had a verb form, knoulechen "acknowledge" (c. 1200), later "find out about; recognize," and "to have sexual intercourse with" (c. 1300); compare acknowledge.
knew: Old English cneow, past tense of know (v.).
gnostic (adj.): "relating to knowledge," especially mystical or esoteric knowledge of spiritual things, 1650s, from Greek gnostikos "knowing, good at knowing, able to discern," from gnostos "known, perceived, understood," earlier gnotos, from gignoskein "learn to know, come to know, perceive; discern, distinguish; observe, form a judgment," from PIE *gi-gno-sko-, reduplicated and suffixed form of root *gno- "to know" (see know (v.)).
notion (n.): late 14c., from Latin notionem (nominative notio) "concept, conception, idea, notice," noun of action from past participle stem of noscere "come to know" (see know). Coined by Cicero as a loan-translation of Greek ennoia "act of thinking, notion, conception," or prolepsis "previous notion, previous conception."
notorious (adj.): 1540s, "publicly known," from Medieval Latin notorius "well-known, commonly known," from Latin notus "known," past participle of noscere "come to know" (see know). Negative connotation arose 17c. from frequent association with derogatory nouns. Related: Notoriously.
notice (n.): early 15c., "information, intelligence," from Middle French notice (14c.), and directly from Latin notitia "a being known, celebrity, fame, knowledge," from notus "known," past participle of (g)noscere "come to know, to get to know, get acquainted (with)," from PIE *gno-sko-, a suffixed form of root *gno- (see know). Sense of "formal warning" is attested from 1590s. Meaning "a sign giving information" is from 1805.
narration (n.): early 15c., from Old French narracion "account, statement, a relating, recounting, narrating, narrative tale," and directly from Latin narrationem (nominative narratio) "a relating, narrative," noun of action from past participle stem of narrare "to tell, relate, recount, explain," literally "to make acquainted with," from gnarus "knowing," from PIE suffixed zero-grade *gne-ro-, from root *gno- "to know" (see know).
note (n.): c. 1300, "a song, music, instrumental music; a musical note," from Latin nota "letter, character, note," originally "a mark, sign, means of recognition," which is perhaps related to notus, past participle of noscere (Old Latin *gnoscere) "to know" (see know). Meaning "notice, attention, reputation" is early 14c. Meaning "brief writing" is from 1540s.
noble (adj.): c. 1200, "illustrious, distinguished; worthy of honor or respect," from Old French noble "of noble bearing or birth," from Latin nobilis "well-known, famous, renowned; excellent, superior, splendid; high-born, of superior birth," earlier *gnobilis, literally "knowable," from gnoscere "to come to know," from PIE root *gno- "to know" (see know). The prominent Roman families, which were "well known," provided most of the Republic's public officials.

Meaning "distinguished by rank, title, or birth" is first recorded late 13c. Sense of "having lofty character, having high moral qualities" is from c. 1600. A noble gas (1902) is so called for its inactivity or intertness; a use of the word that had been applied in Middle English to precious stones, metals, etc., of similar quality (late 14c.), from the sense of "having admirable properties" (c. 1300).
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.
beknow (v.): c. 1300, "to become acquainted with; to be aware or conscious of," from be- + know (v.). Related: Beknown; beknowing.
unknown (adj.): c. 1300, "strange, unfamiliar" (of persons, places), from un- (1) "not" + past participle of know (v.). Compare Old English ungecnawen. In reference to facts, "not discovered or found out," it attested from early 14c. The noun meaning "unknown person" is recorded from 1590s; the unknown "that which is unknown" is from 1650s.
unknowing (adj.): c. 1300, "without knowledge, ignorant," from un- (1) "not" + present participle of know (v.). Noun meaning "ignorance" is mid-14c., especially in phrase cloud of unknowing, title of a medieval book of Christian mysticism. Related: Unknowingly. A verb unknow "fail to recognize" is attested from late 14c.
dunno (v.): colloquial for "(I) don't know," first attested 1842 in American English.
asunder (adv.): mid-12c., contraction of Old English on sundran (see sunder). Middle English used to know asunder for "distinguish, tell apart."
ignorant (adj.): late 14c., "lacking wisdom or knowledge; unaware," from Old French ignorant (14c.), from Latin ignorantem (nominative ignorans) "not knowing, ignorant," present participle of ignorare "not to know, to be unacquainted; mistake, misunderstand; take no notice of, pay no attention to," from assimilated form of in- "not, opposite of" (see in- (1)) + Old Latin gnarus "aware, acquainted with" (source also of Classical Latin noscere "to know," notus "known"), from Proto-Latin suffixed form *gno-ro-, suffixed form of PIE root *gno- "to know" (see know). Also see uncouth.

Form influenced by related Latin ignotus "unknown, strange, unrecognized, unfamiliar." Colloquial sense of "ill-mannered, uncouth, knowing nothing of good manners" attested by 1886. As a noun, "ignorant person," from mid-15c. Related: Ignorantly.
can (v.1): Old English 1st & 3rd person singular present indicative of cunnan "know, have power to, be able," (also "to have carnal knowledge"), from Proto-Germanic *kunnan "to be mentally able, to have learned" (source also of Old Norse kenna "to know, make known," Old Frisian kanna "to recognize, admit," German kennen "to know," Gothic kannjan "to make known"), from PIE root *gno- (see know).

Absorbing the third sense of "to know," that of "to know how to do something" (in addition to "to know as a fact" and "to be acquainted with" something or someone). An Old English preterite-present verb, its original past participle, couth, survived only in its negation (see uncouth), but see also could. The present participle has spun off as cunning.
stuff (n.): early 14c., "quilted material worn under chain mail," from Old French estoffe "quilted material, furniture, provisions" (Modern French étoffe), from estoffer "to equip or stock," which according to French sources is from Old High German stopfon "to plug, stuff," or from a related Frankish word (see stop (v.)), but OED has "strong objections" to this.

Sense extended to material for working with in various trades (c. 1400), then "matter of an unspecified kind" (1570s). Meaning "narcotic, dope, drug" is attested from 1929. To know (one's) stuff "have a grasp on a subject" is recorded from 1927.
Adam: masc. proper name, Biblical name of the first man, progenitor of the human race, from Hebrew adam "man," literally "(the one formed from the) ground" (Hebrew adamah "ground"); compare Latin homo "man," humanus "human," humus "earth, ground, soil." To not know (someone) from Adam "not know him at all" is first recorded 1784.
need (v.): Old English neodian "be necessary, be required (for some purpose); require, have need of," from the same root as need (n.). Meaning "to be under obligation (to do something)" is from late 14c. Related: Needed; needing. The adjectival phrase need-to-know is attested from 1952. Dismissive phrase who needs it?, popular from c. 1960, is a translated Yiddishism.
bean (n.): Old English bean "bean, pea, legume," from Proto-Germanic *bauno (source also of Old Norse baun, Middle Dutch bone, Dutch boon, Old High German bona, German Bohne), and related to Latin faba "bean;" Greek phakos "lentil;" Albanian bathë "horse-bean;" Old Prussian babo, Russian bob "bean," but the original form is obscure; perhaps from a PIE reduplicated base *bha-bha-

As a metaphor for "something of small value" it is attested from c. 1300. Meaning "head" is U.S. baseball slang c. 1905 (in bean-ball "a pitch thrown at the head"); thus slang verb bean meaning "to hit on the head," attested from 1910.

The notion of lucky or magic beans in English folklore is from the exotic beans or large seeds that wash up occasionally in Cornwall and western Scotland, carried from the Caribbean or South America by the Gulf Stream. They were cherished, believed to ward off the evil eye and aid in childbirth.

Slang bean-counter "accountant" recorded by 1971. To not know beans (American English, 1933) is perhaps from the "of little worth" sense, but may have a connection to colloquial expression recorded around Somerset, to know how many beans make five "be a clever fellow."
not: negative particle, mid-13c., unstressed variant of noht, naht "in no way" (see naught). As an interjection to negate what was said before or reveal it as sarcasm, it is first attested 1900; popularized 1989 by "Wayne's World" sketches on "Saturday Night Live" TV show. To not know X from Y (one's ass from one's elbow, shit from Shinola, etc.) was a construction first attested c. 1930. Double negative construction not un- was derided by Orwell, but is persistent and ancient in English, popular with Milton and the Anglo-Saxon poets.
mean (v.1): "intend, have in mind," Old English mænan "to mean, intend, signify; tell, say; complain, lament," from West Germanic *mainijan (source also of Old Frisian mena "to signify," Old Saxon menian "to intend, signify, make known," Dutch menen, German meinen "think, suppose, be of the opinion"), from PIE *meino- "opinion, intent" (source also of Old Church Slavonic meniti "to think, have an opinion," Old Irish mian "wish, desire," Welsh mwyn "enjoyment"), perhaps from root *men- "think" (see mind (n.)). Conversational question you know what I mean? attested by 1834.
knowledgeable (adj.): also knowledgable, c. 1600, "capable of being known, recognizable" (a 17c. sense now obsolete), from knowledge in its Middle English verbal sense + -able. The sense of "having knowledge, displaying mental capacity" is from 1829 and probably a new formation.
rain (n.): Old English regn "rain," from Proto-Germanic *regna- (source also of Old Saxon regan, Old Frisian rein, Middle Dutch reghen, Dutch regen, German regen, Old Norse regn, Gothic rign "rain"), with no certain cognates outside Germanic, unless it is from a presumed PIE *reg- "moist, wet," which may be the source of Latin rigare "to wet, moisten" (see irrigate). Rain dance is from 1867; rain date in listings for outdoor events is from 1948. To know enough to come in out of the rain (usually with a negative) is from 1590s. Rainshower is Old English renscur.
back (n.): Old English bæc "back," from Proto-Germanic *bakam (cognates: Old Saxon and Middle Dutch bak, Old Frisian bek), with no known connections outside Germanic. In other modern Germanic languages the cognates mostly have been ousted in this sense by words akin to Modern English ridge (such as Danish ryg, German Rücken). Many Indo-European languages show signs of once having distinguished the horizontal back of an animal (or a mountain range) from the upright back of a human. In other cases, a modern word for "back" may come from a word related to "spine" (Italian schiena, Russian spina) or "shoulder, shoulder blade" (Spanish espalda, Polish plecy).

To turn (one's) back on (someone or something) "ignore" is from early 14c. Behind (someone's) back "clandestinely" is from late 14c. To know (something) like the back of one's hand, implying familiarity, is first attested 1893. The first attested use of the phrase is from a dismissive speech made to a character in Robert Louis Stevenson's "Catriona":
If I durst speak to herself, you may be certain I would never dream of trusting it to you; because I know you like the back of my hand, and all your blustering talk is that much wind to me.
The story, a sequel to "Kidnapped," has a Scottish setting and context, and the back of my hand to you was noted in the late 19th century as a Scottish expression meaning "I will have nothing to do with you" [see Longmuir's edition of Jamieson's Scottish dictionary]. In English generally, the back of (one's) hand has been used to imply contempt and rejection since at least 1300. Perhaps the connection of a menacing dismissal is what made Stevenson choose that particular anatomical reference.
what (pron.): Old English hwæt, referring to things in abstraction; also "why, wherefore; indeed, surely, truly," from Proto-Germanic pronoun *hwat (source also of Old Saxon hwat, Old Norse hvat, Danish hvad, Old Frisian hwet, Dutch wat, Old High German hwaz, German was, Gothic hva "what"), from PIE *kwod, neuter singular of *kwos "who" (see who). Corresponding to Latin quid.

Meaning "what did you say?" is recorded from c. 1300. As an adjective and adverb, in Old English. As a conjunction in late Old English. Exclamatory use was in Old English. What the _____ (devil, etc.) as an exclamation of surprise is from late 14c. As an interrogative expletive at the end of sentences from 1891; common in affected British speech. Or what as an alternative end to a question is first attested 1766. What have you "anything else one can think of" is from 1925. What's up? "what is happening?" first recorded 1881.

"To give one what for is to respond to his remonstrant what for? by further assault" [Weekley]. The phrase is attested from 1873; what for? as introducing a question is from 1760. To know what is what is from c. 1400; I'll tell you what to emphasize what is about to be said is in Shakespeare.
hit (v.): late Old English hyttan, hittan "come upon, meet with, fall in with, 'hit' upon," from a Scandinavian source such as Old Norse hitta "to light upon, meet with," also "to hit, strike;" Swedish hitta "to find," Danish and Norwegian hitte "to hit, find," from Proto-Germanic *hitjan, which is of uncertain origin. Meaning shifted in late Old English period to "strike, come into forcible contact" via the notion of "to reach with a blow or missile," and the word displaced Old English slean (modern slay) in this sense. Original sense survives in phrases such as hit it off (1780, earlier in same sense hit it, 1630s) and is revived in slang hit on (1970s).

To hit the bottle "drink alcohol" is from 1933 (hit the booze in the same sense is from 1889, and hit the pipe "smoke opium" is also late 19c.). To figuratively hit the nail on the head (1570s) is from archery. To hit the hay "go to bed" is from 1912. Hit the road "leave" is from 1873; hit the bricks is from 1909, originally trade union jargon meaning "go out on strike." To hit (someone) up "request something" is from 1917. To not know what hit (one) is from 1923. Related: Hitting.
rope (n.): Old English rap "rope, cord, cable," from Proto-Germanic *raipaz (source also of Old Norse reip, West Frisian reap, Middle Dutch, Dutch reep "rope," Old Frisian silrap "shoe-thong," Gothic skauda-raip "shoe-lace," Old High German, German reif "ring, hoop"). Technically, only cordage above one inch in circumference and below 10 (bigger-around than that is a cable). Nautical use varies. Finnish raippa "hoop, rope, twig" is a Germanic loan-word.

To know the ropes (1840, Dana) originally is a seaman's term. Phrase on the ropes "defeated" is attested from 1924, a figurative extension from the fight ring, where ropes figure from 1829. To be at the end of (one's) rope "out of resources and options" is first attested 1680s. Formerly also in many slang and extended uses related to punishment by hanging, such as John Roper's window "a noose," rope-ripe "deserving to be hanged," both 16c. To give someone (enough) rope (to hang himself) is from 1650s.
wot (v.): "to know" (archaic), from Old English wat, first and third person singular present indicative of witan "to know" (see wit (v.)).
con (n.2): "study," early 15c., from Old English cunnan "to know, know how" (see can (v.1)).
weet (v.): "to know" (archaic), 1540s, from Middle English weten, variant of witen "to know" (see wit (v.)).
place (n.): c. 1200, "space, dimensional extent, room, area," from Old French place "place, spot" (12c.) and directly from Medieval Latin placea "place, spot," from Latin platea "courtyard, open space; broad way, avenue," from Greek plateia (hodos) "broad (way)," fem. of platys "broad" (see plaice (n.)).

Replaced Old English stow and stede. From mid-13c. as "particular part of space, extent, definite location, spot, site;" from early 14c. as "position or place occupied by custom, etc.; position on some social scale;" from late 14c. as "inhabited place, town, country," also "place on the surface of something, portion of something, part," also, "office, post." Meaning "group of houses in a town" is from 1580s.

Also from the same Latin source are Italian piazza, Catalan plassa, Spanish plaza, Middle Dutch plaetse, Dutch plaats, German Platz, Danish plads, Norwegian plass. Wide application in English covers meanings that in French require three words: place, lieu, and endroit. Cognate Italian piazza and Spanish plaza retain more of the etymological sense.

To take place "happen" is from mid-15c. To know (one's) place is from c. 1600; hence figurative expression put (someone) in his or her place (1855). Place of worship attested from 1689, originally in official papers and in reference to assemblies of dissenters from the Church of England. All over the place "in disorder" is attested from 1923.
cognoscence (n.): mid-15c., from Latin cognoscere "to get to know, recognize" (see cognizance).
nescient (adj.): 1620s, from Latin nescientem (nominative nesciens) "ignorant, unaware," present participle of nescire "not to know, to be ignorant," from ne "not" + scire "to know" (see science).
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.
let (v.): Old English lætan (Northumbrian leta) "to allow; to leave behind, depart from; leave undone; bequeath," also "to rent, put to rent or hire" (class VII strong verb; past tense let, leort, past participle gelæten), from Proto-Germanic *letan (source also of Old Saxon latan, Old Frisian leta, Dutch laten, Old High German lazan, German lassen, Gothic letan "to leave, let"), from PIE *led-, extended form of root *le- (2) "to let go, slacken" (source also of Latin lassus "faint, weary," Lithuanian leisti "to let, to let loose;" see lenient). If that derivation is correct, the etymological sense would be "let go through weariness, neglect."

"The shortening of the root vowel ... has not been satisfactorily explained" [OED]. Of blood, from late Old English. Other Old and Middle English senses include "regard as, consider; behave toward; allow to escape; pretend;" to let (someone) know and to let fly (arrows, etc.) preserve the otherwise obsolete sense of "to cause to." To let (someone) off "allow to go unpunished, excuse from service" is from 1814. To let on is from 1725 as "allow (something) to be known, betray one's knowledge of," 1822 as "pretend" (OED finds a similar use in the phrase never let it on him in a letter from 1637). To let out is late 12c. as "allow to depart" (transitive); intransitive use "be concluded," of schools, meetings, etc., is from 1888, considered by Century Dictionary (1902) to be "Rural, U.S." Of garments, etc., late 14c.

Let alone "abstain from interfering with" is in Old English; the phrase in the sense "not to mention, to say nothing of" is from 1812. To let (something) be "leave it alone" is from c. 1300; let it be "let it pass, leave it alone" is from early 14c. To let go is from c. 1300 as "allow to escape," 1520s as "cease to restrain," 1530s as "dismiss from one's thoughts." Let it go "let it pass, no matter" is as old as Chaucer's Wife of Bath: "But age allas Hath me biraft my beautee Lat it go, far wel, the deuel go ther with!" [c. 1395]. Let me see "show me" is from c. 1300.
prescience (n.): late 14c., from Old French prescience (13c.) and directly from Late Latin praescientia "fore-knowledge," from *praescientem, present participle of *praescire "to know in advance," from Latin prae "before" (see pre-) + scire "to know" (see science).
cun (v.): "to learn to know, inquire into," from Old English cunnian "to learn to know," ultimately from the same ancient root as can (v.1). Surviving into 17c. and perhaps later in dialects.
cognition (n.): mid-15c., "ability to comprehend," from Latin cognitionem (nominative cognitio) "a getting to know, acquaintance, knowledge," noun of action from past participle stem of cognoscere "to get to know, recognize" (see cognizance).
ulema (n.): "scholars of Muslim religious law," 1680s, from Arabic 'ulema "learned men, scholars," plural of 'alim "learned," from 'alama "to know."