indecipherable (adj.) Look up indecipherable at Dictionary.com
1802, from in- (1) "not" + decipherable (see decipher (v.)). Undecipherable is older. Related: Indecipherably; indecipherability.
indecision (n.) Look up indecision at Dictionary.com
1735, from in- (1) "not, opposite of, without" + decision. Perhaps from or modeled on French indécision (17c.), which Cotgrave's "French and English Dictionary" (1673) translates with An undecision.
indecisive (adj.) Look up indecisive at Dictionary.com
1726, "inconclusive," from in- (1) "not, opposite of" + decisive. Meaning "vacillating, characterized by indecision" is from 1775. Related: Indecisively; indecisiveness.
indeclinable (adj.) Look up indeclinable at Dictionary.com
late 14c., originally in grammar, from French indéclinable or directly from Latin indeclinabilis "unchangeable," also in grammar, from indeclinatus "unchanged, constant," from in- "not, opposite of" (see in- (1)) + declinatus, from declinare "to lower; avoid, deviate; bend from, inflect" (see decline (v.)). Related: Indeclinably.
indecorous (adj.) Look up indecorous at Dictionary.com
1680s, "in bad taste," from Latin indecorus "unbecoming, unseemly, unsightly; disgraceful," from in- "not, opposite of, without" (see in- (1)) + decorus "becoming, fitting, seemly, proper" (see decorous). Related: Indecorously; indecorousness (1670s).
indecorum (n.) Look up indecorum at Dictionary.com
1570s, from Latin indecorum, noun use of neuter of adjective indecorus "unbecoming, unseemly, unsightly" (see indecorous).
indeed (adv.) Look up indeed at Dictionary.com
c. 1600, a contraction into one word of the prepositional phrase in dede "in fact, in truth" (early 14c.), from Old English dæd "a doing, act, action, event" (see deed (n.)). As an interjection, 1590s; as an expression of surprise or disgust, 1834. Emphatic form yes (or no) indeedy attested from 1856, American English.
indefatigability (n.) Look up indefatigability at Dictionary.com
1630s, from indefatigable + -ity. Indefatigableness is from 1650s; indefatigation from 1640s.
indefatigable (adj.) Look up indefatigable at Dictionary.com
1580s (implied in indefatigably), from French indefatigable (15c.), from Latin indefatigabilis "that cannot be wearied," from in- "not" (see in- (1)) + defatigare "to tire out," from de- "utterly, down, away" (see de-) + fatigare "to weary" (see fatigue (n.)).

Blount's "Glossographia" (1656) has defatigable, which also was in use elsewhere in 17c., but the modern use of defatigable (1948) probably is a jocular back-formation from indefatigable.
indefeasible (adj.) Look up indefeasible at Dictionary.com
"not to be set aside or overcome," 1530s (implied in indefeasibly), from in- (1) "not, opposite of" + defeasible (see defeasance).
indefensible (adj.) Look up indefensible at Dictionary.com
1520s, "that cannot be maintained or justified by argument," from in- (1) "not, opposite of" + defensible. From 1560s as "that cannot be maintained by force." Related: Indefensibly.
indefinability (n.) Look up indefinability at Dictionary.com
1814, from indefinable + -ity.
indefinable (adj.) Look up indefinable at Dictionary.com
"incapable of being exactly described," 1721, from in- (1) "not, opposite of" + definable (see define). Related: Indefinably.
indefinite (adj.) Look up indefinite at Dictionary.com
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]
indefinitely (adv.) Look up indefinitely at Dictionary.com
early 15c., "without settled limitation, boundless;" see indefinite + -ly (2).
indeliberation (n.) Look up indeliberation at Dictionary.com
1610s; see in- (1) "not, opposite of" + deliberation.
indelible (adj.) Look up indelible at Dictionary.com
1520s, from Latin indelebilis "indelible, imperishable," from in- "not, opposite of, without" (see in- (1)) + delebilis "able to be destroyed," from delere "destroy, blot out" (see delete). Vowel change from -e- to -i- in English is late 17c. Related: Indelibly.
indelicacy (n.) Look up indelicacy at Dictionary.com
1712, from indelicate + -cy.
indelicate (adj.) Look up indelicate at Dictionary.com
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]
indemnification (n.) Look up indemnification at Dictionary.com
1732, "action of compensating for loss or damage," noun of action from indemnify.
indemnify (v.) Look up indemnify at Dictionary.com
"compensate for loss or expense," 1610s, from Latin indemnis "unhurt" (see indemnity) + -fy. Related: Indemnified; indemnifying. "Indemnify formerly meant to save a person from damage or loss, but now much more often means to make good after loss or the damage of property." [Century Dictionary]
indemnity (n.) Look up indemnity at Dictionary.com
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.
indemonstrable (adj.) Look up indemonstrable at Dictionary.com
1560s, from in- (1) "not, opposite of" + demonstrable.
indent (v.1) Look up indent at Dictionary.com
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.
indent (v.2) Look up indent at Dictionary.com
"to dent or press in," c. 1400, from in (adv.) + dent (v.). Etymologically distinct from indent (v.1) but felt as the same.
indent (n.) Look up indent at Dictionary.com
"cut or notch in a margin," 1590s, from indent (v.1). A supposed earlier noun sense of "a written agreement" (late 15c.) is described in Middle English Dictionary as "scribal abbrev. of endenture."
indentation (n.1) Look up indentation at Dictionary.com
"cut, notch, incision," 1728, of margins or edges, extended form of indent (n.).
indentation (n.2) Look up indentation at Dictionary.com
"action of making a dent or impression; small hollow or depression, slight pit," 1847, from indent (v.2).
indention (n.) Look up indention at Dictionary.com
1763, formed irregularly from indent (v.1). It could be a useful word if it split with indentation the two senses (relating to marginal notches and to dents) of that word, but indention, too, is used in both.
indenture (n.) Look up indenture at Dictionary.com
late 14c., endenture, indenture, "written formal contract for services (between master and apprentice, etc.), a deed with mutual covenants," from Anglo-French endenture, Old French endenteure "indentation," from endenter "to notch or dent" (see indent (v.1)).

Such contracts (especially between master craftsmen and apprentices) were written in full identical versions on a sheet of parchment, which was then cut apart in a zigzag, or "notched" line. Each party took one, and the genuineness of a document of indenture could be proved by laying it beside its counterpart.
indenture (v.) Look up indenture at Dictionary.com
1650s, "enter into a covenant;" 1670s, "bind by indenture," from indenture (n.). It was used earlier in a sense "to wrinkle, furrow" (1630s). Related: indentured; indenturing.
indentured (adj.) Look up indentured at Dictionary.com
"bound by indenture," 1748 (in indentured servant), past participle adjective from indenture (v.).
independence (n.) Look up independence at Dictionary.com
1630s, "fact of not depending on others or another, self-support and self-government;" see independent + -ence. Earlier in same sense was independency (1610s). U.S. Independence Day (July 4, commemorating events of 1776) is recorded under that name by 1791.

An Old English word for it was selfdom, with self + dom "law," but in form this is closer to privilege (n.). The two concepts are not always distinguishable.
independent (adj.) Look up independent at Dictionary.com
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."
indescribable (adj.) Look up indescribable at Dictionary.com
1726, from in- (1) "not, opposite of" + describable (see describe). Related: Indescribably; indescribability (1797). In same sense, Old English had unasecgendlic. Indescribables for "trousers" (1819) was colloquial in England for a generation or so.
We cannot omit here to state, that, some years since, we recollect a rumour in the gallery [of the House of Commons], that Madame de Staël was sitting, en habit d'homme, in a surtout and military indescribables, listening to the debate, under the protection of Sir J. Macintosh. ["Privileges of Women," in "Retrospective Review," London, 1824]
See inexpressible.
indescript (adj.) Look up indescript at Dictionary.com
"undescribed," 1831, from in- (1) "not, opposite of" + Latin descriptus, past participle of describere (see describe).
indestructibility (n.) Look up indestructibility at Dictionary.com
1670s, from indestructible + -ity.
indestructible (adj.) Look up indestructible at Dictionary.com
early 15c., from in- (1) "not, opposite of" + destructible. Related: Indestructibly.
indeterminable (adj.) Look up indeterminable at Dictionary.com
late 15c., from Late Latin indeterminabilis "that cannot be defined," from in- "not" (see in- (1)) + determinabilis "that can be defined," from determinare "to enclose, bound, set limits to" (see determine). Related: Indeterminably.
indeterminacy (n.) Look up indeterminacy at Dictionary.com
1640s, see indeterminate + -acy.
indeterminate (adj.) Look up indeterminate at Dictionary.com
late 14c., from Late Latin indeterminatus "undefined, unlimited," from in- "not, opposite of" (see in- (1)) + determinatus, past participle of determinare "to enclose, bound, set limits to" (see determine). Related: Indeterminately.
indetermination (n.) Look up indetermination at Dictionary.com
1640s, from in- (1) "not, opposite of" + determination.
indeterminism (n.) Look up indeterminism at Dictionary.com
1874 in philosophy, from in- (1) "not, opposite of" + determinism.
index (v.) Look up index at Dictionary.com
"compile an index," 1720, from index (n.). Related: Indexed; indexing.
index (n.) Look up index at Dictionary.com
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.
indexation (n.) Look up indexation at Dictionary.com
1960, in reference to rates of wages, prices, etc. pegged to a specified index of economic activity, noun of action from index (v.).
India Look up India at Dictionary.com
"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.) Look up Indian at Dictionary.com
"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 Ocean Look up Indian Ocean at Dictionary.com
first attested 1515 in Modern Latin (Oceanus Orientalis Indicus), named for India, which projects into it; earlier it was the Eastern Ocean, as opposed to the Western Ocean (Atlantic) before the Pacific was surmised.
Indian summer (n.) Look up Indian summer at Dictionary.com
"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).