Online Etymology Dictionary

indefinable (adj.): "incapable of being exactly described," 1721, from in- (1) "not, opposite of" + definable (see define). Related: Indefinably.
indefinite (adj.): 1520s, "not precise, vague," from Latin indefinitus "indefinite," from in- "not, opposite of, without" (see in- (1)) + definitus, past participle of definire (see define). In reference to number, "The term was introduced by Pascal. Descartes distinguished between the indefinite, which has no particular limit, and the infinite which is incomparably greater than anything having a limit. The distinction is considered as highly important by many metaphysicians." [Century Dictionary]
indelicate (adj.): 1670s, "offensive to a refined sense of propriety, beyond the bounds of proper reserve," from in- (1) "not, opposite of" + delicate. Related: Indelicately.
Immorality and indelicacy are different things. Rabelais is indelicate to the last degree, but he is not really immoral. Congreve is far less indelicate, but far more immoral. [James Hadley, "Essays Philological and Critical," 1873]
indemnity (n.): mid-15c., "security or exemption against damage, loss, etc.," from Middle French indemnité (14c.), from Late Latin indemnitatem (nominative indemnitas) "security for damage," from Latin indemnis "unhurt, undamaged," from in- "not, opposite of, without" (see in- (1)) + damnum "damage" (see damn). Meaning "legal exemption" is from 1640s; sense of "compensation for loss" is from 1793. Related: Indemnitor; indemnitee.
indent (v.1): early 15c., indenten, endenten "to make notches; to give (something) a toothed or jagged appearance," also "to make a legal indenture, make a written formal agreement or contract," from Old French endenter "to notch or dent, give a serrated edge to" (12c.) and directly from Medieval Latin indentare "to furnish with teeth," from in- "into, in, on, upon" (see in- (2)) + verb from Latin dens (genitive dentis) "tooth" (see tooth).
An indented document was usually, if not always, written in two or more identical versions. Orig. these were written on a single sheet of parchment and then cut apart along a zigzag, or 'indented' line. Each party to the agreement retained one copy, which he could readily authenticate by matching its serrate edge with that of another copy. [Middle English Dictionary]
The printing sense "insert white space to force text inward" is first attested 1670s. Related: Indented (late 14c.); indenting.
independent (adj.): 1610s, "not dependent on something else," from in- (1) "not, opposite of" + dependent. French independant is attested from c. 1600; Italian independente from 1590s. In English originally of churches, nations; in reference to persons from 1660s. Meaning "able to live well without labor" is from 1732. Meaning "unbiased, set up so as to be unaffected by outside influence" is from 1790. Related: Independently.

As a noun, from 1640s as "member of an independent congregational church, English Congregationalist." It is attested from 1670s as "one who acts according to his own will" and 1808 in the specific sense "person not acting as part of a political party."
indestructible (adj.): early 15c., from in- (1) "not, opposite of" + destructible. Related: Indestructibly.
index (n.): late 14c., "the forefinger," from Latin index (genitive indicis) "one who points out, discloser, discoverer, informer; forefinger (because used in pointing); pointer, sign; title, inscription, list," literally "anything which points out," from indicare "to point out" (see indication). Related: Indexical.

Obsolete in English in its original sense (index finger is recorded from 1768). Meaning "alphabetical list of a book's contents with directions where in the text to find them" is from late 16c., from Latin phrases such as Index Nominum "Index of Names."

Meaning "object serving as a pointer on an instrument, hand of a clock or watch" is from 1590s. Scientific sense (refractive index, etc.) is from 1829, from notion of "an indicator." Economic sense (cost-of-living index, etc.) is from 1870, from the scientific usage.

The Church sense of "forbidden books" is from index librorum prohibitorum, first published 1564 by authority of Pius IV. The Index Expurgatorius was the catalogue of books that Catholics were forbidden to read unless certain passages were deleted, first printed 1571.
India: "the Indian subcontinent, central Asia south of the Himalayas," formerly sometimes used generally for "Asia;" since 1947 specifically in reference to the Republic of India, Old English India, Indea, from Latin India, from Greek India "region of the Indus River," later used of the region beyond it, from Indos "Indus River," also "an Indian," from Old Persian Hindu, the name for the province of Sind, from Sanskrit sindhu "river."

The more common Middle English form was Ynde or Inde, from Old French (hence Indies). The form India began to prevail again in English from 16c., perhaps under Spanish or Portuguese influence.
Indian (adj., n.): "inhabit of India or South Asia; pertaining to India," c. 1300 (noun and adjective), from Late Latin indianus, from India (see India). Applied to the aboriginal native inhabitants of the Americas from at least 1553 as a noun (1610s as an adjective), reflecting Spanish and Portuguese use, on the mistaken notion that America was the eastern end of Asia (it was also used occasionally 18c.-19c. of inhabitants of the Philippines and indigenous peoples of Australia and New Zealand. The Old English adjective was Indisc, and Indish (adj.) was common in 16c.

Red Indian, to distinguish the native Americans from inhabitants of India, is first attested 1831 in British English (Carlyle) but was not commonly used in North America. More than 500 modern phrases include Indian, most of them U.S. and most impugning honesty or intelligence, such as Indian gift:
An Indian gift is a proverbial expression, signifying a present for which an equivalent return is expected. [Thomas Hutchinson, "History of Massachusetts Bay," 1765]
Hence Indian giver "one who gives a gift and then asks for it back" (1848). Indian elephant is from c. 1600; Indian corn is from 1620s; to walk Indian file is from 1758. Indian club is from 1824 as a weapon, 1825 as exercise equipment (clubs were noted noted in Lewis & Clark, etc., as characteristic weapons of native warriors in the American West). Indian-head (adj.) in reference to U.S. copper pennies with a portrait of an Indian in profile, from 1862.
Indian summer (n.): "spell of warm, dry, hazy weather after the first frost" (happening anywhere from mid-September to nearly December, according to location), 1774, North American English (also used in eastern Canada), perhaps so called because it was first noted in regions then still inhabited by Indians, in the upper Mississippi valley west of the Appalachians, or because the Indians first described it to the Europeans. No evidence connects it with the color of fall leaves, or to a season of renewed Indian attacks on settlements due to renewed warm weather (a widespread explanation dating at least to the 1820s).

It is the American version of British All-Hallows summer, French été de la Saint-Martin (feast day Nov. 11), etc. Also colloquial was St. Luke's summer (or little summer), period of warm weather occurring about St. Luke's day (Oct. 18).
indication (n.): early 15c., "a sign, that which indicates," from Latin indicationem (nominative indicatio) "an indicating; valuation," noun of action from past participle stem of indicare "point out, show," from in- "into, in, on, upon" (see in- (2)) + dicare "proclaim" (see diction).
indict (v.): formerly also endict, c. 1300, enditen, inditen, "bring formal charges against (someone); accuse of a crime," from Anglo-French enditer "accuse, indict, find chargeable with a criminal offense" (late 13c.), Old French enditier, enditer "to dictate, write, compose; (legally) indict," from Vulgar Latin *indictare "to declare, accuse, proclaim in writing," from in- "in" (see in- (2)) + Latin dictare "to say, compose in words" (see dictate (v.)).

Later 14c. non-legal senses "write, compose (a poem, etc.); dictate" have gone with the older form, endite (q.v.). Retained its French pronunciation after the spelling was re-Latinized c. 1600. The sense is perhaps partly confused with Latin indicare "to point out." In classical Latin, indictus meant "not said, unsaid" (from in- "not"). Related: Indictable; indicted; indicting.
indie (n.): "independent record company," 1945, shortening of independent. Among the earliest mentioned were Continental, Majestic, and Signature. Used of film production companies since 1920s, of theaters from 1942; extended by 1984 to a type of pop music issued by such labels.
Indies: "India and adjacent regions and islands," 1550s, plural of Indie, Indy, from Middle English Ynde (early 13c.), the usual word in Middle English for "India," from the Old French form of Latin India (see India). Commonly applied to Asia and the East generally; later in a time of geographical confusion, it was applied to the Caribbean basin, which was distinguished from Asia proper by being called the West Indies.
indifferent (adj.): late 14c., "unbiased, impartial, not preferring one to the other" (of persons), "alike, equal" (of things), from Old French indifferent "impartial" or directly from Latin indifferentem (nominative indifferens) "not differing, not particular, of no consequence, neither good nor evil," from in- "not, opposite of" (see in- (1)) + differens, present participle of differre "set apart" (see differ). Extended sense of "apathetic, no more inclined to one thing than to another" first recorded early 15c.; that of "neither good nor bad" is from 1530s, on notion of "neither more nor less advantageous," but since 17c. it has tended toward "rather bad."
indigenous (adj.): "born or originating in a particular place," 1640s, from Late Latin indigenus "born in a country, native," from Latin indigena "sprung from the land, native," as a noun, "a native," literally "in-born," or "born in (a place)," from Old Latin indu (prep.) "in, within" + gignere (perfective genui) "beget," from PIE root *gene- "to produce, give birth, beget" (see genus).

Indu "within" is from archaic endo, which is cognate with Greek endo- "in, within," from PIE *endo-, extended form of root *en "in" (see in (adv.)). Related: Indigenously.
indigence (n.): late 14c., from Old French indigence "indigence, need, privation" (13c.), from Latin indigentia "need, want; insatiable desire," from indigentem (nominative indigens) "in want of, needing," present participle of indigere "to need, stand in need of," from indu "in, within" (see indigenous) + egere "be in need, want," from PIE *eg- "to lack" (source also of Old Norse ekla "want, lack," Old High German eccherode "thin, weak").
indigestion (n.): late 14c., "difficulty or inability in digesting food," from Old French indigestion (13c.), from Late Latin indigestionem (nominative indigestio), from in- "not, opposite of" (see in- (1)) + digestionem "arrangement, distribution" (see digestion). An Old English word for it was unmeltung.
Nimzo-Indian (adj.): type of defensive opening in chess, 1935, in reference to Aron Nimzowitsch (1886-1935), Latvian-born Jewish chess genius who popularized it, a variation of the Indian defense (late 19c.) attributed to Indian chess player Moheschunder Bannerjee.
red ink (n.): "financial losses," 1929, from the red ink traditionally used to indicate debits in accounts.
Dies Irae: literally "day of wrath," first words of Latin hymn of Last Judgment, attributed to Thomas of Celano (c. 1250). See diurnal + ire.
injunction (n.): early 15c., from Late Latin iniunctionem (nominative iniunctio) "a command," noun of action from past participle stem of Latin iniungere "impose, inflict, bring upon," literally "attach to," from in- "on" (see in- (2)) + iungere "to join" (see jugular).
injury (n.): late 14c., "harm, damage, loss; a specific injury," from Anglo-French injurie "wrongful action" (Old French injure, 13c.), from Latin iniuria "wrong, an injustice, insult, unlawful violence, assault, damage, harm," noun use of fem. of iniurius "wrongful, unjust, unlawful," from in- "not, opposite of" (see in- (1)) + ius (genitive iuris) "right, law" (see jurist).
injustice (n.): late 14c., from Old French injustice "unfairness, injustice" (14c.), from Latin iniustitia "unfairness, injustice," from iniustus "unjust, wrongful, unreasonable, improper, oppressive," from in- "not" (see in- (1)) + iustus "just" (see just (adj.)). Injust (adj.) is attested from late 15c., from French, but unjust is the usual English word.
ink (n.): "the black liquor with which men write" [Johnson], mid-13c., from Old French enche, encre "dark writing fluid" (12c.), earlier enque (11c.), originally enca, from Late Latin encaustum, from Late Greek enkauston. This is the neuter of the past-participle adjective enkaustos "burned in," from the stem of enkaiein "to burn in," from en- "in" (see en- (1)) + kaiein "to burn" (see caustic).

In Pliny the word is the name of a kind of painting executed by fire or heat. Later it was the name of the purple-red ink, the sacrum encaustum, used by the Roman emperors to sign their documents; this was said to have been obtained from the ground remains of certain shellfish, formed into writing fluid by the application of fire or heat, which explained the name. In the Code of Justinian, the making of it for common uses, or by common persons, was prohibited under penalty of death and confiscation of goods.
It denoted a kind of painting practised by the ancients, in which the crayon was dipped in wax of various colours. Encausto pingere is to practise this art, paint in encaustic or enamel. Encaustum afterwards came to signify an ink for the purpose of writing; and the "sacred encaustum" of Justinian's Code was an ink which the Roman Emperors used for imperial subscriptions. It was of the imperial colour, reddish purple, and was made of the purple dye, prepared in some way by the application of fire. (So that in this use of the word, the notion of burning which there is in the etymology, is still retained.) [from footnote in "The Life, Letters, and Sermons of Bishop Herbert de Losinga," Oxford, 1878]
The usual words for "ink" in Latin was atramentum (source of Old French arrement), literally "anything that serves to dye black," from ater "black;" the Greek word was melan, neuter of melas "black." The Old English word for it was blæc, literally "black," and compare Swedish bläk, Danish blæk "ink." Spanish and Portuguese (tinta) and German (tinte) get their "ink" words from Latin tinctus "a dyeing."

Donkin credits a Greek pronunciation, with the accent at the front of the word, for the French evolution; the same Latin word, behaving regularly, became inchiostro (with excrescent -r-) in Italian, encausto in Spanish. As an adjective, inken (c. 1600) occasionally has been used. Ink-slinger, contemptuous for "journalist," is from 1870. The psychologist's ink-blot test attested from 1915.
inkhorn (n.): late 14c., "small portable vessel (originally made of horn) for holding ink," from ink (n.) + horn (n.). Used attributively from 1540s ("Soche are your Ynkehorne termes," John Bale) as an adjective for things (especially vocabulary) supposed to be beloved by scribblers, pedants, and bookworms. An Old English word for the thing was blæchorn.
inkling (n.): c. 1400, apparently from the gerund of the Middle English verb inclen "utter in an undertone, hint at, hint" (mid-14c.), which is of unknown origin; perhaps it is related to Old English inca "doubt, suspicion, question, scruple." However the earliest record of the word is as a nyngkiling; and Middle English Dictionary offers that this is not a misdivision of an inkling but rather suggests the word is a nasalized variant of nikking "a hint, slight indication," gerundive of the Middle English verb nikken "to mark (a text) for correction" (mid-15c.), from nik (n.) "a notch, tally" (see nick (n.)).
inlaid (adj.): 1590s, "embedded in (something)," from in + laid, past participle of lay (v.). In old slang (c. 1700) it meant "full of money, living at ease."
inland (adj.): "of or pertaining to interior parts of a country," 1550s, from in + land (n.). The noun meaning "interior parts of a country (remote from the sea or borders)" is attested from 1570s. Meaning "confined to a country" (as opposed to foreign) is from 1540s. In Middle English and Old English the same compound meant "land immediately around the mansion of an estate, land in the lord's own occupation (as opposed to land occupied by tenants)." Related: Inlander.
in-law (n.): 1894, "anyone of a relationship not natural," abstracted from father-in-law, etc.
The position of the 'in-laws' (a happy phrase which is attributed ... to her Majesty, than whom no one can be better acquainted with the article) is often not very apt to promote happiness. ["Blackwood's Magazine," 1894]
The earliest recorded use of the formation is in brother-in-law (13c.); the law is Canon Law, which defines degrees of relationship within which marriage is prohibited. Thus the word originally had a more narrow application; its general extension to more distant relatives of one's spouse is, according to OED "recent colloquial or journalistic phraseology." Middle English inlaue (13c.) meant "one within or restored to the protection and benefit of the law" (opposite of an outlaw), from a verb inlauen, from Old English inlagian "reverse sentence of outlawry."
inlet (n.): "narrow opening into a coast, arm of the sea," 1570s, said by old sources to be originally a Kentish term; a special use of Middle English inlate "passage or opening by which an enclosed place may be entered" (c. 1300), from inleten "to let in" (early 13c.), from in + let (v.).
in loco parentis: legal Latin, 1640s in English, literally "in the place of a parent," from loco, ablative of locus "a place" (see locus (n.)) + parentis, genitive of parens "parent" (see parent (n.)).
inmate (n.): 1580s, "one allowed to live in a house rented by another" (usually for a consideration), from in (adj.) "inside" + mate (n.) "companion." OED suggests the first element is perhaps originally inn. Sense of "one confined to an institution" is first attested 1834.
in medias res: Latin, literally "in the midst of things," from medias, accusative fem. plural of medius "middle" (see medial (adj.)) + accusative plural of res "a thing," from PIE *re- "to bestow, endow." From Horace, in reference to narrative technique:
Semper ad eventum festinat, et in medias res,
Non secus ac notas auditorem rapit (etc.)
inn (n.): Old English inn "lodging, dwelling, house," probably from inne (adv.) "inside, within" (see in). Meaning "public house with lodging" is perhaps by c. 1200, certainly by c. 1400. Meaning "lodging house or residence for students" is attested from early 13c. in Anglo-Latin, now obsolete except in names of buildings that were so used (such as Inns of Court, mid-15c.).
innards (n.): "entrails of an animal," 1825, innerds, dialectal variant of inwards "the bowels" (c. 1300); see inward. Compare inmeat "edible entrails of animals" (c. 1400); Old English innoð "entrails, stomach."
innate (adj.): early 15c., "existing from birth," from Late Latin innatus "inborn, native, natural" (source also of French inné, Spanish and Italian innato), past participle of innasci "to be born in, originate in," from in- "in" (see in- (2)) + nasci "to be born" (Old Latin gnasci; see genus). Opposed to acquired. Related: Innately; innateness.
inner (adj.): c. 1400, from Old English inra, comparative of inne (adv.) "inside" (see in (adv.)). Similar formation in Old High German innaro, German inner. The original order of comparison was in/inner/inmost; the evolution has been unusual for a comparative, and inner has not been used with than since Middle English.

Inner man "the soul" is from late Old English. The Quaker inner light is attested by that name from 1833. Inner tube in the pneumatic tire sense is from 1894. Inner city is attested from 1690s; as a euphemism for "urban poverty and crime," from 1963.
inning (n.): Old English innung "a taking in, a putting in," gerundive of innian "get within, put or bring in; lodge; include; fill up, restore," from inn (adv.) "in" (see in). Meaning "a team's turn in action in a game" first recorded 1735, usually plural in cricket, singular in baseball.
innocent (adj.): mid-14c., "doing no evil; free from sin, guilt, or moral wrong," from Old French inocent "harmless; not guilty; pure" (12c.), from Latin innocentem (nominative innocens) "not guilty, blameless; harmless; disinterested," from in- "not" (see in- (1)) + nocentem (nominative nocens), present participle of nocere "to harm," from *nok-s-, suffixed form of PIE root *nek- (1) "death" (see necro-).

Meaning "free from guilt of a specific crime or charge" is from late 14c., as is the meaning "with childlike simplicity or artlessness." Humorous sense "free, devoid of" is from 1706. The noun meaning "person who is innocent of sin or evil, artless or simple person" is from c. 1200, especially a young child (who presumably has not yet sinned actively). The Holy Innocents (early 14c.) were the young children slain by Herod after the birth of Jesus (Matt. ii:16), hence Innocents day (Dec. 28).

Indo-European words for "innocent" are generally negative compound of the word for "guilty." An exception is the Germanic group represented by Gothic swikns (also "pure, chaste"), Old Norse sykn "free from guilt, innocent" (especially as a law term), Old English swicn "clearance from a charge," also "cleansing," but these are of uncertain origin.
innocuous (adj.): 1590s, from Latin innocuus "harmless; innocent; inoffensive," from in- "not" (see in- (1)) + nocuus "hurtful," from root of nocere "to injure, harm," from *nok-s-, suffixed form of PIE root *nek- (1) "death" (see necro-). Related: Innocuously; innocuousness.
innovate (v.): 1540s, "introduce as new" (trans.), from Latin innovatus, past participle of innovare "to renew, restore;" also "to change," from in- "into" (see in- (2)) + novus "new" (see new). Intransitive meaning "bring in new things, alter established practices" is from 1590s. Related: Innovated; innovating.
innuendo (n.): "oblique hint, indiscreet suggestion," usually a deprecatory one, 1670s, from Latin innuendo "by meaning, pointing to," literally "giving a nod to," ablative of gerund of innuere "to mean, signify," literally "to nod to," from in- "at" (see in- (2)) + nuere "to nod" (see numinous).

Originally in English a legal phrase (1560s) from Medieval Latin, with the sense of "to wit," introducing an explanatory or parenthetical clause, it also introduced the derogatory meaning alleged in libel cases, which led to broader meaning. As a verb, from 1706.
Innuit: 1765, from Inupiaq Eskimo inuit "the people," plural of inuk "man, person."
innumerable (adj.): mid-14c., from Latin innumerabilis "countless, immeasurable," from in- "not" (see in- (1)) + numerabilis "able to be numbered," from numerare "to count, number," from numerus "a number" (see number (n.)). Related: Innumerability.
inoculate (v.): mid-15c., "implant a bud into a plant," from Latin inoculatus, past participle of inoculare "graft in, implant a bud or eye of one plant into another," from in- "in" (see in- (2)) + oculus "bud," originally "eye" (see eye (n.)). Meaning "implant germs of a disease to produce immunity" is from inoculation, originally in reference to smallpox, after 1799, often used in sense of "to vaccine inoculate." Related: Inoculated; inoculating.
inopportune (adj.): 1530s, from Late Latin inopportunus "unfitting," from in- "not" + opportunus "favorable, convenient" (see opportune). Rare or obsolete in 18c. Related: Inopportunely; inopportuneness; inopportunity.
inordinate (adj.): late 14c., "not ordered, lacking order or regularity," from Latin inordinatus "unordered, not arranged," from in- "not, opposite of" (see in- (1)) + ordinatus, past participle of ordinare "to set in order" (see order (n.)). Sense of "immoderate, excessive" is from notion of "not kept within orderly limits." Related: Inordinately; inordinateness.
input (n.): 1753, "a sum (of cash) put in, a sharing, contribution," from verbal phrase; see in (adv.) + put (v.). Meaning "energy supplied to a device or machine" is from 1902, later of electronic devices; computing sense of "data fed into a machine" is from 1948, though this is perhaps from the verb in the computing sense.