insatiability (n.) Look up insatiability at Dictionary.com
1650s, from Late Latin insatiabilitas, from insatiabilis (see insatiable).
insatiable (adj.) Look up insatiable at Dictionary.com
early 15c., insaciable, from Old French insaciable (13c.), or directly from Late Latin insatiabilis "not to be satisfied," from in- "not, opposite of" (see in- (1)) + satiabilis, from satiare (see satiate). Related: Insatiably.
insatiate (adj.) Look up insatiate at Dictionary.com
mid-15c., insaciate, from Latin insatiatus "unsatisfied," from in- "not, opposite of" (see in- (1)) + satiatus, past participle of satiare (see satiate).
inscribe (v.) Look up inscribe at Dictionary.com
1550s (form inscriven is from late 14c.), from Latin inscribere "to write in or on," (see inscription). Meaning "to dedicate (by means of an inscription)" is from 1640s. Related: Inscribed; inscribing.
inscription (n.) Look up inscription at Dictionary.com
late 14c., from Latin inscriptionem (nominative inscriptio) "a writing upon, inscription," noun of action from past participle stem of inscribere "inscribe, to write on or in anything," from in- "in" (see in- (2)) + scribere "to write" (see script (n.)).
inscrutability (n.) Look up inscrutability at Dictionary.com
1650s, from inscrutable + -ity.
inscrutable (adj.) Look up inscrutable at Dictionary.com
c.1500, from Late Latin inscrutabilis, from in- "not, opposite of" (see in- (1)) + scrutabilis, from scrutari "examine, ransack" (see scrutiny). Related: Inscrutably.
insect (n.) Look up insect at Dictionary.com
c.1600, from Latin (animal) insectum "(animal) with a notched or divided body," literally "cut into," from neuter past participle of insectare "to cut into, to cut up," from in- "into" (see in- (2)) + secare "to cut" (see section (n.)). Pliny's loan-translation of Greek entomon "insect" (see entomology), which was Aristotle's term for this class of life, in reference to their "notched" bodies.

First in English in 1601 in Holland's translation of Pliny. Translations of Aristotle's term also form the usual word for "insect" in Welsh (trychfil, from trychu "cut" + mil "animal"), Serbo-Croatian (zareznik, from rezati "cut"), Russian (nasekomoe, from sekat "cut"), etc.
insecticide (n.) Look up insecticide at Dictionary.com
"substance which kills insects," 1865, from insect + -cide.
insectivore (n.) Look up insectivore at Dictionary.com
1863, from French insectivore (1817), from Latin insectivorus, from comb. form of insectum (see insect) + vorare "devour, swallow" (see voracity).
insectivorous (adj.) Look up insectivorous at Dictionary.com
1610s; see insect + -vorous.
insecure (adj.) Look up insecure at Dictionary.com
1640s, "unsafe," from Medieval Latin insecurus, from in- "not" (see in- (1)) + Latin securus (see secure). Psychological sense dates from 1935; insecurity in this sense dates from 1917. Related: Insecurely.
insecurity (n.) Look up insecurity at Dictionary.com
1640s, from Medieval Latin insecuritas, from insecurus (see insecure). Specific psychological sense is by 1917.
inseminate (v.) Look up inseminate at Dictionary.com
1620s, "to cast as seed," from Latin inseminatus, past participle of inseminare "to sow, implant," from in- "in" (see in- (2)) + semen (genitive semenis) "seed." Meaning "to impregnate with semen" is attested from 1923. Related: Inseminated; inseminating.
insemination (n.) Look up insemination at Dictionary.com
1650s, "action of sowing," noun of action from inseminate. Meaning "infusion of semen" is from 1860.
insensate (adj.) Look up insensate at Dictionary.com
1510s, from Late Latin insensatus "irrational, foolish," from Latin in- "not" (see in- (1)) + sensatus "gifted with sense" (see sensate). Insensate means "not capable of feeling sensation," often "inanimate;" insensible means "lacking the power to feel with the senses," hence, often, "unconscious;" insensitive means "having little or no reaction to what is perceived by one's senses," often "tactless."
insense (v.) Look up insense at Dictionary.com
"cause (someone) to understand," c.1400, ensense, from Old French ensenser "to enlighten, to bring to sense," from en- "in" (see in- (2)) + sens (see sense (n.)). Restricted to Northern English dialect from 17c.
insensibility (n.) Look up insensibility at Dictionary.com
late 14c., from Late Latin insensibilitas, from Latin insensibilis (see insensible).
insensible (adj.) Look up insensible at Dictionary.com
c.1400, "lacking the power to feel with the senses," from Latin insensibilis "that cannot be felt," from in- "not" (see in- (1)) + sensibilis (see sensible). Also sometimes in Middle English "incapable of being felt or perceived by the senses" (early 15c.). Meaning "unconscious" is attested from early 15c. See insensate.
insensibly (adv.) Look up insensibly at Dictionary.com
early 15c.; see insensible + -ly (2).
insensitive (adj.) Look up insensitive at Dictionary.com
c.1600, "having little or no reaction to what is perceived by one's senses," from in- (1) "not, opposite of" + sensitive. For sense, see insensate. Meaning "without consideration for the feelings of others" attested by 1975. Related: Insensitively.
inseparability (n.) Look up inseparability at Dictionary.com
1620s, from Late Latin inseparabilitas, from Latin inseparabilis (see inseparable).
inseparable (adj.) Look up inseparable at Dictionary.com
mid-14c., from Latin inseparabilis "that cannot be separated," from in- "not, opposite of" (see in- (1)) + separabilis, from separare (see separate (v.)). Related: Inseparably.
insert (v.) Look up insert at Dictionary.com
"to set in, put or place in," 1520s, from insert, past participle of Middle English inseren "to set in place, to graft, to introduce (into the mind)" (late 14c.), from Latin inserere "to put in, implant," from in- "in" (see in- (2)) + serere "join together" (see series). Related: Inserted; inserting. The noun meaning "something inserted" is from 1893.
insertion (n.) Look up insertion at Dictionary.com
1590s, "act of putting in," from Late Latin insertionem (nominative insertio), noun of action from past participle stem of inserere (see insert). Meaning "that which is inserted" attested from 1620s.
inservice (adj.) Look up inservice at Dictionary.com
also in-service, 1928, from in + service.
inset (n.) Look up inset at Dictionary.com
1550s, "influx of water, place where water flows in," from in + set (n.2). Meaning "extra pages of a book, etc." is from 1875; that of "small map in the border of a larger one" is from 1881.
inshallah Look up inshallah at Dictionary.com
1857, phonetic spelling of Arabic in sha Allah "if Allah wills (it)."
inside (n.) Look up inside at Dictionary.com
late 14c., ynneside "interior of the body," compound of in (adv.) + side (n.). The adjective is 1610s, from the noun. Inside job "robbery, espionage, etc., committed by or with the help of a resident or servant of a place" is attested by 1887, American English (also, late 19c., early 20c., "indoors work"). Inside track "advantage" is metaphoric because those lanes are shorter on a curved track. Inside of, in reference to time, is from 1839.
inside-out (adj.) Look up inside-out at Dictionary.com
"with the in side being out," c.1600, from inside + out (adv.).
insider (n.) Look up insider at Dictionary.com
"one in possession of special information by virtue of being within some organization," 1848, from inside + -er (1). Originally in reference to the stock markets.
insidious (adj.) Look up insidious at Dictionary.com
1540s, from Middle French insidieux (15c.) or directly from Latin insidiosus "deceitful, cunning, artful," from insidiae (plural) "plot, snare, ambush," from insidere "sit on, occupy," from in- "in" (see in- (2)) + sedere "to sit" (see sedentary). Related: Insidiously; insidiousness.
insight (n.) Look up insight at Dictionary.com
c.1200, innsihht, "sight with the eyes of the mind," mental vision, understanding," from in + sight. Sense shaded into "penetrating understanding into character or hidden nature" (1580s).
insightful (adj.) Look up insightful at Dictionary.com
1881, from insight + -ful. Related: Insightfully; insightfulness.
insignia (n.) Look up insignia at Dictionary.com
1640s, from Latin insignia, neuter plural of insigne "badge, mark," from in- "in" (see in- (2)) + signum "mark" (see sign). Singular is insigne.
insignificance (n.) Look up insignificance at Dictionary.com
1690s, from insignificant + -ance. Related: Insignificancy (1650s).
insignificant (adj.) Look up insignificant at Dictionary.com
1650s, from in- (1) "not, opposite of" + significant. Related: Insignificantly.
insincere (adj.) Look up insincere at Dictionary.com
1620s (implied in insincerely), from Latin insincerus "not genuine, not pure, adulterated," from in- "not" (see in- (1)) + sincerus (see sincere).
insincerity (n.) Look up insincerity at Dictionary.com
1540s, from Latin insincerus (see insincere) + -ity.
insinuate (v.) Look up insinuate at Dictionary.com
1520s, from Latin insinuatus, past participle of insinuare "to throw in, push in, make a way; creep in, intrude, bring in by windings and curvings, wind one's way into," from in- "in" (see in- (2)) + sinuare "to wind, bend, curve," from sinus "a curve, winding" (see sinus). Sense of "to introduce tortuously or indirectly" is from 1640s. Related: Insinuated; insinuating; insinuatingly.
insinuation (n.) Look up insinuation at Dictionary.com
1520s, from Latin insinuationem (nominative insinuatio) "entrance through a narrow way; an ingratiating oneself," noun of action from past participle stem of insinuare (see insinuate).
insipid (adj.) Look up insipid at Dictionary.com
1610s, "without taste or perceptible flavor," from French insipide (16c.), from Late Latin inspidus "tasteless," from Latin in- "not" (see in- (1)) + sapidus "tasty," from sapere "have a taste" (also "be wise;" see sapient). Figurative meaning "uninteresting, dull" first recorded 1640s, but it was also a secondary sense in Medieval Latin.
In ye coach ... went Mrs. Barlow, the King's mistress and mother to ye Duke of Monmouth, a browne, beautifull, bold, but insipid creature. [John Evelyn, diary, Aug. 18, 1649]
Related: Insipidly.
insipidity (n.) Look up insipidity at Dictionary.com
c.1600, from insipid + -ity.
insipience (n.) Look up insipience at Dictionary.com
early 15c., "lack of wisdom, foolishness," from Old French insipience, from Latin insipientia "folly," from insipientem (see insipient).
insipient (adj.) Look up insipient at Dictionary.com
"foolish," mid-15c., from Latin insipientem (nominative insipiens) "unwise, foolish," from in- "not" (see in- (1)) + sapientem (see sapient). "Now mostly, or wholly, disused to avoid confusion with incipient" [OED].
insist (v.) Look up insist at Dictionary.com
1580s, from Latin insistere "persist, dwell upon, stand upon," from in- "upon" (see in- (2)) + sistere "take a stand" (see assist). Perhaps in some cases a back-formation from insistence. Related: Insisted; insisting.
insistence (n.) Look up insistence at Dictionary.com
mid-15c., from Middle French insister (see insist) + -ence.
insistent (adj.) Look up insistent at Dictionary.com
1620s, "standing on something," from Latin insistentem (nominative insistens), present participle of insistere (see insist). Meaning "dwelling firmly on something asserted" is from 1868. Related: Insistently.
insobriety (n.) Look up insobriety at Dictionary.com
1610s, from in- (1) "not, opposite of" + sobriety.
insolate (v.) Look up insolate at Dictionary.com
"to expose to the rays of the sun," 1620s, from Latin insolatus, past participle of insolare, from in- "in" (see in- (2)) + sol "sun" (see Sol). Related: Insolated; insolation.