Online Etymology Dictionary

tie-in (n.): "connection," 1934, from verbal phrase (attested by 1793), from tie (v.) + in (adv.).
trade-in (n.): 1917, in reference to used cars, from verbal phrase, from trade (v.) + in (adv.).
fill-in (n.): "substitute," 1918 (as an adjective, 1916), from verbal phrase; see fill (v.), in (adv.). Earlier as a noun was fill-up (1811).
flat-iron (n.): "iron for smoothing," 1810, from flat (adj.) + iron (n.). Applied to triangular or wedge-shaped buildings from 1862.
father-in-law (n.): late 14c., from father (n.) + in-law.
insectivorous (adj.): 1610s; see insect + -vorous. The mammalian class of Insectivora is from 1821; insectivore (n.) is from 1858 (both are earlier in French).
walk-in (adj.): 1928, "without appointment," from the verbal phrase, from walk (v.) + in (adv.). As a noun, meaning "walk-in closet," by 1946.
water-ice (n.): "sugared water, flavored and frozen," 1818, from water (n.1) + ice (n.).
well-informed (adj.): mid-15c., from well (adv.) + past participle of inform (v.).
West Indies: Caribbean islands explored by Columbus, 1550s, reflecting the belief (or hope) that they were western outliers of the Indies of Asia. Related: West Indian, which is from 1580s in reference to the native inhabitants, 1650s in reference to European settlers there, and 1928 in reference to people of West Indian ancestry.
inelegance (n.): 1690s, from French inélégance (16c.) or directly from Late Latin inelegantia, from in- "not, opposite of" (see in- (1)) + Latin elegantia "taste, propriety, refinement" (see elegance).
inequal (adj.): late 14c., from Old French inequal (14c.), from Latin inaequalis "unequal," from in- "not, opposite of" (see in- (1)) + aequalis "equal" (see equal).
inerrable (adj.): "incapable of erring," 1610s, from Late Latin inerrabilis "unerring," from in- "not, opposite of" (see in- (1)) + errabilis, from Latin errare "to wander; to err" (see err). Related: Inerrability "infallibility" (1620s).
inexpediency (n.): 1640s; see inexpedient + -cy.
in facie curiae: "before the court," legal Latin, from ablative of Latin facies "form, face" (see face (n.)). + genitive of curia "court" (see curia).
inexpungible (adj.): 1610s, from in- (1) "not, opposite of" + expungible (see expunge).
inextirpable (adj.): 1620s, from in- (1) "not, opposite of" + extirpable (see extirpate).
infecund (adj.): early 15c., from Latin infecundus, from in- "not, opposite of" (see in- (1)) + fecundus (see fecund). Related: Infecundity.
infortunate (adj.): "unlucky, luckless," late 14c., from Latin infortunatus, from in- "not, opposite of" (see in- (1)) + fortunatus "prospered, prosperous; lucky, happy" (see fortunate (adj.)). Also used in medieval astrology in reference to the supposed malevolent influence of certain positions or combinations of planets. The word lies beneath the "obsolete" headstone in OED. Related: infortune (n.); infortunacy.
informational (adj.): 1810, from information + -al (1).
inflected (adj.): 1640s, "bent, curved," past-participle adjective from inflect (v.). Grammatical sense is from 1775.
infold (n.): see enfold. Related: Infolded; infolding.
informed (adj.): 1540s, "current in information," past-participle adjective from inform (v.). In 16c.-17c. it also could mean "unformed, formless," from in- (1) "not, opposite of," and was used in astronomy of stars that did not form part of the visual pattern of a constellation but were within it.
inflatable (adj.): 1821, from inflate + -able.
infuriating (adj.): 1874, present participle adjective from infuriate (v.). Related: Infuriatingly.
ingrained (adj.): "deeply rooted," 1590s, literally "dyed with grain "cochineal," the red dyestuff (see engrain). Figuratively, "thoroughly imbued" (of habits, principles, prejudices, etc.) from 1851. In reference to dyed carpets, etc., it is attested from 1766, from the manufacturing phrase in (the) grain "in the raw material before manufacture."
in-gather (v.): also ingather, 1570s, from in (adv.) + gather (v.). Related: Ingathered; ingathering (1530s).
ingle (n.2): "boy favorite, catamite," 1590s, of uncertain origin.
ingraft (v.): see engraft. Related: ingrafted; ingrafting.
ingrave (v.): see engrave. Related: Ingraved; ingraving.
ingurgitation (n.): "immoderate eating and drinking," 1520s, from Late Latin ingurgitationem (nominative ingurgitatio), noun of action from past participle stem of Latin ingurgitare "plunge into, gorge," from in- "in, into" (see in- (2)) + gurgitare "to engulf," from gurges "whirlpool, gorge" (see gurges).
Ingvaeonic (n.): hypothetical ancestral North Sea Germanic language, 1933, from Latin Ingaeuones, name of a Germanic tribe in Tacitus, literally "people of Yngve," god, demigod, or eponymous ancestor. Earlier the word was used in English in reference to North Sea Germanic tribes (1904).
inhesion (n.): 1630s, from Late Latin inhaesionem (nominative inhaesio) "a hanging or adhering to," noun of action from past participle stem of Latin inhaerere "to stick in or into" (see inherent).
initiand (n.): "one about to be initiated," 1913, from Latin initiand, gerundive of initiare "to begin, initiate; instruct in mysteries" (see initiate (v.)).
initialese (n.): "abbreviation by use of initials," 1950, from initial (n.) + -ese.
in-itselfness (n.): 1879, in philosophy; see in (adv.) + itself + -ness.
injector (n.): 1727, agent noun from inject (v.).
ink-well (n.): also inkwell, 1854, from ink (n.) + well (n.). A schoolroom implement, so called because it sat down in the surface of a desk in contrast to an ink-stand.
inlapidate (v.): "turn to stone" (trans.), 1620s, from in- (2) "in, into" + verb from Latin lapis (genitive lapidis) "stone" (see lapideous). Related: Inlapidated; inlapidating.
inlier (n.): 1859, from in (adv.) on model of outlier.
inlighten (v.): former alternative form of enlighten (q.v.). Related: Inlightened; inlightening.
innominable (adj.): "unnameable," late 14c., from Old French innominable, from Late Latin innominabilis "that cannot be named," from in- "not, opposite of" (see in- (1)) + *nominabilis, from Latin nominalis "pertaining to a name or names," from nomen (genitive nominis) "name"(see name (n.)). In jocular use, innominables = "trousers" (1827; see inexpressible).
inofficious (adj.): c. 1600, "neglecting one's duty;" in law, "not in accord with one's moral duty," 1660s, from Medieval Latin inofficiosus "contrary to duty; harmful," from in- "not, opposite of" (see in- (1) + Latin officiosus "dutiful, obliging" (see officious).
innumerate (adj.): "unacquainted with the basic principles of mathematics," 1959, based on illiterate, with Latin numerus "a number" (see number (n.)). Related: Innumeracy.
Ino: Greek sea-goddess, daughter of Cadmus and Hermione.
-ino: word-ending in some English words from Spanish and Portuguese (albino, casino, etc.), the Spanish and Portuguese form of -ine (1), from Latin -inus/-inum.
inquiline (n.): 1640s, "a lodger," from Latin inquilinus "an inhabitant of a place not his own," from *incolinus, from incola "an inhabitant," from in- "in" (see in- (2)) + colere "inhabit, dwell" (see colony). Zoological sense of "animal living in the abode of another, a commensal" is from 1865.
input (v.): late 14c., "put on, impose," from in (adv.) + put (v.). Modern sense "feed data into a machine" is from 1946, a new formation from the same elements.
inquiring (adj.): "given to inquiry or investigation," 1590s, present-participle adjective from inquire (v.). Related: Inquiringly.
i.n.r.i.: ecclesiastical inscription, it stands for Iesus Nazarenus, Rex Iudaeorum ("Jesus of Nazareth, King of the Jews," John xix:19).