Online Etymology Dictionary

insectarium (n.): 1872, from insect + -arium, abstracted from aquarium, etc.
infuriation (n.): 1791, noun of action from infuriate (v.).
ingratiation (n.): 1804, noun of action from ingratiate (v.).
insensuous (adj.): "not affecting the senses," 1851, from in- (1) "not, opposite of" + sensuous. Related: Insensuously; insensuousness.
inshore (adj.): also in-shore, "near the shore," 1701, from in (prep.) + shore (n.). As an adverb from 1737.
insert (n.): "something inserted," 1893, especially a paper, etc., placed in among the pages of a newspaper, magazine, etc., from insert (v.).
insinuating (adj.): "wheedling, ingratiating," 1590s, present-participle adjective from insinuate (v.). Related: Insinuatingly.
insolation (n.): "exposure to the sun's rays," 1610s, from French insolation (16c.), from Latin insolationem (nominative insolatio), noun of action from past participle stem of insolare "place in the sun, expose to the sun," from in- "in" (see in- (2)) + sol "sun" (see Sol).
insociability (n.): 1740, from insociable "unsociable" (1580s), from in- (1) "not, opposite of" + sociable.
insolvable (adj.): 1650s, from French insolvable (15c.), from in- "not, opposite of" (see in- (2)) + solvable (see solvable).
inspectorate (n.): 1762, "function or office of an inspector," from inspector + -ate (1). From 1853 as "district under the supervision of an inspector."
interflow (n.): "a flowing into each other," 1839, from inter- + flow (n.).
interfold (v.): 1570s, from inter- + fold (v.). Related: Interfolded; interfolding.
interleaf (n.): "extra page in a book," usually left blank and for taking notes, 1741, from inter- "between" + leaf (n.).
intercommunion (n.): 1749, "intimate intercourse, fellowship," from inter- "between" + communion (n.).
intercommunicate (v.): 1580s, "communicate reciprocally," from inter- + communicate (v.) or else from Medieval Latin intercommunicatus, past participle of intercommunicare.
intercollegiate (adj.): 1873, from inter- + collegiate.
interconnectedness (n.): 1873, noun of state from past participle of interconnect + -ness. Interconnection is attested from 1827.
intercommunication (n.): mid-15c., "discussion, conference," from Anglo-Latin intercommunicationem; see inter- + communication). Attested from 1881 in reference to systems of linked telephones.
intercept (n.): "that which is intercepted," from intercept (v.). From 1821 of a ball thrown in a sport; 1880 in navigation; 1942 in reference to secret messages.
interamnian (adj.): "between two rivers" (usually, if not exclusively, with reference to Mesopotamia), 1774, from Late Latin interamnius, from inter "between" (see inter-) + amnis "a river," a word perhaps of Celtic origin (see afanc).
interblend (v.): "intermingle," 1823, from inter- + blend (v.). Related: Interblended; interblending.
intentioned (adj.): "having intentions" (of a specified kind), 16c., from intention + -ed.
intended (n.): "one's intended husband or wife," 1767, noun use of past participle of intend (v.).
intellection (n.): c. 1400, intellecioun "meaning, purpose;" mid-15c., "the understanding;" 1610s, "an act of understanding," from Old French intelleccion and directly from Medieval Latin intellectionem (nominative intellectio), noun of action from past participle stem of Latin intelligere "to understand, discern" (see intelligence).
insusceptible (adj.): c. 1600; see in- (1) "not, opposite of" + susceptible (adj.). Perhaps modeled on French insusceptible (16c.).
inspired (adj.): c. 1400, "communicated by divine or supernatural powers," past-participle adjective from inspire (v.). From 1660s as "infused with seemingly supernatural influence."
inspissation (n.): c. 1600, from Medieval Latin inspissationem (nominative inspissatio), noun of action from past participle stem of inspissare, from in- "in, into" (see in- (2)) + Latin spissare "to thicken," related to spissus "thick" (see spissitude).
insufflation (n.): 1570s, in ecclesiastical use, "a breathing upon," to symbolize the influence of the Holy Ghost or to expel evil spirits, from Late Latin insufflationem (nominative insufflatio) "a blowing into," noun of action from past participle stem of insufflare, from in- "in, into" (see in- (2)) + sufflare "blow from below," from assimilated form of sub- "under, below" (see sub-) + flare "to blow" (see blow (v.1)). Medical sense of "a blowing of air into" (the lungs) is from 1821; that sense is found earlier in French.
insularism (n.): 1828, from insular in the figurative sense + -ism.
insulting (adj.): "containing or inflicting insult," 1590s, present-participle adjective from insult (v.). Related: insultingly.
instance (v.): "cite as an instance" (in the logical sense), c. 1600, from instance (n.). Middle English had a verb instauncen "to plead with, urge, entreat." Related: Instanced; instancing.
instanter (adv.): "instantly," 1680s, from Latin instanter "urgently, pressingly," in Medieval Latin, "presently, at once," from Latin instans "present, pressing, urgent," literally "standing near" (see instant (adj.)).
instellation (n.): "a putting among the stars," 1795, from in- (2) "in" + noun of action from Latin stellare "to set with stars," from stella (see star (n.)). Perhaps modeled on earlier French instellation.
instauration (n.): "restoration, renewal," c. 1600, from Latin instaurationem (nominative instauratio) "a renewal," noun of action from last participle stem of instaurare, from in- "in" (see in- (2)) + -staurare (ending also found in restaurant), from PIE *stau-ro-, from root *stā- "to stand, set down, make or be firm," with derivatives meaning "place or thing that is standing" (see stet).
instructible (adj.): c. 1600, from instruct + -ible.
instreaming (adj.): 1855, from in (adv.) + streaming. As a noun from 1876.
instrumentary (adj.): "of or pertaining to a deed or legal instrument," 1722, from instrument (n.) in the legal sense.
insurable (adj.): 1786, from insure (v.) + -able. Related: Insurability.
interfacial (adj.): 1837, of crystals, from inter- "between" + facial (adj.).
interlanguage (n.): "artificial or auxilliary language," 1927, from inter- + language.
intermediacy (n.): 1713, from intermediate + -cy. Intermediateness is from 1826.
intermediation (n.): c. 1600, noun of action from intermediate (v.).
interlingual (adj.): "between or relating to two languages," 1854, from inter- "between" + lingual. Related: Interlingually.
intermigration (n.): "reciprocal migration," 1670s, from inter- "between" + migration.
interminate (adj.): 1530s, from Latin interminatus "unbounded, endless," from in- "not" (see in- (1)) + terminalis "pertaining to a boundary or end, final," from terminus "end, boundary line" (see terminus).
interministerial (adj.): 1917, in reference to branches of government, from inter- "between" + ministerial.
intermissive (adj.): "not continuous," 1580s, from Latin intermiss-, past participle stem of intermittere "leave off, leave an interval" (see intermit).
intermitting (adj.): "stopping at intervals," 1620s, present-participle adjective from intermit (v.). Related: Intermittingly.
internee (n.): "one who is interned," from intern (v.1) + -ee.