Online Etymology Dictionary

inside-out (adj.): "with the in side being out," c. 1600, from inside (n.) + out (prep.).
insipidity (n.): c. 1600, from insipid + -ity.
insipience (n.): early 15c., "lack of wisdom, foolishness," from Old French insipience (15c.) or directly from Latin insipientia "folly, unwisdom," from insipientem "unwise, foolish" (see insipient).
insolubility (n.): 1754, "incapability of dissolving in a liquid," 1791, from Late Latin insolubilitas, from Latin insolubilis "that cannot be loosened" (see insoluble). Earlier in a sense "that cannot be dissolved" (of marriage), 1610s. The meaning "that cannot be solved" (1722) probably is a separate formation from insoluble.
insobriety (n.): 1610s, from in- (1) "not, opposite of" + sobriety.
insomuch (adv.): late 14c. as a phrase; tending to be run together from 16c.; see in (adv.) + so + much, and compare inasmuch.
instatement (n.): "act of instating," 1670s, from instate + -ment.
instructional (adj.): 1801, from instruction + -al (1).
instrumentalist (n.): "musical performer on an instrument," 1818, from instrumental in the musical sense + -ist. Perhaps from German Instrumentalist (18c.).
insubstantiality (n.): 1827, from insubstantial + -ity.
insularity (n.): 1755, "narrowness of feelings," from insular in the metaphoric sense + -ity. Sense of "state of being an island" (from the classical sense) attested from 1784, in reference to explorations of Australia and New Zealand.
insurrectionary (adj.): 1796, from insurrection + -ary. As a noun from 1893. Earlier adjectives were insurrectional (1794), insurrective (1590s), insurrectious (1630s). Insurrectionist (n.) is from 1811.
insult (n.): c. 1600, "an attack;" 1670s as "an act of insulting, contemptuous treatment," from Middle French insult (14c.) or directly from Late Latin insultus "insult, scoffing," noun use of past participle of insilire, literally "to leap at or upon" (see insult (v.)). The older noun was insultation (1510s). To add insult to injury translates Latin injuriae contumeliam addere.
in't: archaic or poetic contraction of in it, attested from 17c. I'nt, also i'n't, as a contraction of is not is recorded from 1742.
intellectualize (v.): 1819 (Coleridge), "infuse with intellectual quality," from intellectual + -ize. From 1827 as "exercise the mind, reason upon a matter of intellect." Related: Intellectualized; intellectualizing.
intellectualization (n.): 1821, noun of action from intellectualize.
intelligencer (n.): 1580s, "spy, informant," agent noun from intelligence. Perhaps modeled on French intelligencier or Italian intelligentiere. Meaning "bringer of news, one who conveys intelligence" is from 1630s; as a newspaper name from 1640s.
intelligibility (n.): 1670s, from intelligible + -ity.
interceptor (n.): 1590s, from Latin interceptor "interceptor, usurper, embezzler," agent noun from intercipere (see intercept (v.)). As a type of fast fighter aircraft, from 1930. Intercepter is attested from c. 1600.
intercalation (n.): 1570s, from Latin intercalationem (nominative intercalatio) "insertion of an intercalary day," noun of action from past participle stem of intercalare "proclaim an intercalary day" (see intercalate). The general sense "insertion of any addition into an existing series" is from 1640s.
intercrural (adj.): "between the thighs," or in medicine, "between leg-like structures," 1690s, from inter- "between" + Latin crus "shin, shank, (lower) leg; supports of a bridge," from Proto-Italic *krus-, which is of uncertain origin.
intercoastal (adj.): "within the coasts," 1927, from inter- + coastal.
interchange (n.): early 15c., "an exchange, act of exchanging reciprocally," from Old French entrechange, from entrechangier (see interchange (v.)). Meaning "alternate succession" is from 1550s. In reference to a type of road junction, 1944.
interdependency (n.): 1830, from interdependent + -cy.
interdependent (adj.): 1817 (Coleridge), from inter- + dependent. Related: Interdependently.
interest (v.): "cause to be interested, engage the attention of," c. 1600, earlier interesse (1560s), from the noun (see interest (n.)). Perhaps also from or influenced by interess'd, past participle of interesse.
interested (adj.): 1660s, "characterized by concern or sympathy," past-participle adjective from interest (v.). From 1828 as "having an interest or stake (in something);" sense "motivated by self-interest" (1705) is perhaps a back-formation from disinterested. Related: Interestedness.
interferometer (n.): "instrument for measuring the interference of light waves," 1897, a hybrid from interfere + -meter. Compare interferential (1867), coined on the model of differential. Related: Interferometric; interferometry.
interfaith (adj.): 1921, from inter- + faith.
interglacial (adj.): 1867 in reference to warm spells between ice ages, from German, coined 1865 by Swiss naturalist Oswald Heer (1809-1883); see inter- "between" + glacial. The word was used earlier in reference to situations between glaciers or ice caps (1835).
interjacent (adj.): 1590s, from Latin interiacentem (nominative interiacens) "lying between," present participle of interiacere "to lie between," from inter- (see inter-) + iacere "to throw; to set, establish" (see jet (v.)). Related: Interjacency.
interiority (n.): 1701, from interior + -ity.
interior (n.): "part of a country distant from the coast," 1796, from interior (adj.); meaning "internal part, inside" is from 1828. Meaning "internal affairs of a country or state" (as in U.S. Department of the Interior) is from 1826. The Latin adjective also was used as a noun.
interlinear (adj.): late 14c., "situated between the lines," from Medieval Latin interlinearis "that which is between the lines," from inter- (see inter-) "between" + Latin linearis (see linear). Meaning "having interpolated lines" is from 1620s. Related: Interlineary.
intermesh (v.): 1863, in reference to gears, from inter- "between" + mesh (v.). Related: Intermeshed; intermeshing.
intermediate (v.): c. 1600, "to interfere;" 1620s, "to mediate," from inter- "between" + mediate (v.). Related: Intermediated; intermediating.
interlocution (n.): "interchange of speech, dialogue, action of talking and replying," 1530s, from Latin interlocutionem (nominative interlocutio) "a speaking between, interlocution," noun of action from past participle stem of interloqui "to speak between; to interrupt" (see interlocutor).
intermeddle (v.): late 14c., entremedlen, "to mix together, blend," from Anglo-French entremedler, Old French entremesler; from inter- + Anglo-French medler (see meddle (v.)). From early 15c. as "involve oneself in what is not one's business."
intermarriage (n.): 1570s, "act or fact of marrying" (now mostly restricted to legal use), from inter- + marriage. Meaning "marriage between members of different classes, tribes, etc." is from c. 1600.
intermittence (n.): 1796, from intermittent + -ence. Perhaps from French. Intermittency is from 1660s.
intermix (v.): 1550s (implied in intermixed), from inter- "between" + mix (v.). Originally transitive; intransitive sense is from 1722. Related: Intermixt; intermixing.
intermixture (n.): 1580s, "that which is mixed;" 1590s, "action of intermixing;" see inter- + mixture (n.).
interpenetrate (v.): 1809, from inter- "between" + penetrate (v.). Related: Interpenetrated; interpenetrating.
interpenetration (n.): 1809, from inter- + penetration.
interpolator (n.): 1650s, from Late Latin interpolator "one who corrupts or spoils," agent noun from past participle stem of Latin interpolare "to polish; to alter; to falsify" (see interpolate).
interpunction (n.): "punctuation, a point inserted in writing," 1610s, from Latin interpunctionem (nominative interpunctio) "a putting of points between (words), division by points," noun of action from past participle stem of interpungere "to put points between," from inter- "between" (see inter-) + pungere "to prick, pierce," related to pugnus "a fist" (see pugnacious).
interleague (adj.): also inter-league, by 1917 in a U.S. baseball sense, from inter- "between" + league (n.). Earlier (1580s) as a verb, "to combine in a league."
investigable (adj.): "that may be investigated," c. 1400, from Late Latin investigabilis "that may be searched into," from Latin investigare "trace out, search after," from in- "in, into" (see in- (2)) + vestigare "to track, trace," from vestigium "footprint, track" (see vestige).
interpretable (adj.): 1610s, from Late Latin interpretabilis "that can be explained or translated," from Latin interpretari "explain, expound, understand" (see interpret).
interrupt (n.): "action of interrupting," 1956, originally in computing in reference to programs, from interrupt (v.).