Online Etymology Dictionary

inconvertible (adj.): 1640s, from in- (1) "not, opposite of" + convertible (adj.). Related: Inconvertibly.
incorporate (v.): late 14c., "to put (something) into the body or substance of (something else), blend; absorb, eat," also "solidify, harden," often in medical writing, from Late Latin incorporatus, past participle of incorporare "unite into one body, embody, include," from Latin in- "into, in, on, upon" (see in- (2)) + verb from corpus (genitive corporis) "body" (see corporeal).

Meaning "to legally form a body politic with perpetual succession and power to act as one person, establish as a legal corporation" is from mid-15c. Intransitive sense of "unite with another body so as to become part of it" is from 1590s. Related: Incorporated; incorporating.
incorporation (n.): late 14c., incorporacioun, "act or process of combining substances; absorption of light or moisture," from Old French incorporacion or directly from Late Latin incorporationem (nominative incorporatio) "an embodying, embodiment," noun of action from past participle stem of incorporare "unite into one body" (see incorporate (v.)). Meaning "the formation of a corporate body (such as a guild) by the union of persons, forming an artificial person," is from early 15c.
Incorporation, n. The act of uniting several persons into one fiction called a corporation, in order that they may be no longer responsible for their actions. A, B and C are a corporation. A robs, B steals and C (it is necessary that there be one gentleman in the concern) cheats. It is a plundering, thieving, swindling corporation. But A, B and C, who have jointly determined and severally executed every crime of the corporation, are blameless. [Ambrose Bierce, 1885]
incorporeal (adj.): early 15c., "spiritual, immaterial," with -al (1) and Late Latin incorporeus "without body," from in- "not" (see in- (1)) + adjective from corpus (genitive corporis) "body" (see corporeal). The Old French adjective was incorporel. Glossed in Old English as lichhaemleas (see lich).
incorrect (adj.): early 15c., "uncorrected, not chastened into obedience," of sinners, etc. (a sense now obsolete), from Latin incorrectus "uncorrected, not revised," from in- "not" (see in- (1)) + correctus, past participle of corrigere "to put straight; to reform" (see correct (v.)). Sense of "not in good style" is from 1670s; that of "factually wrong, erroneous, inaccurate" is from 1750s (implied in incorrectly).
incorrigibility (n.): late 15c., from incorrigible + -ity.
incorrigible (adj.): mid-14c., "incurable (of diseases, venom, etc.); extravagant (of expense); implacable (of hearts)," from Old French incorrigible "perfect, beyond rebuke or discipline" (14c.) or directly from Latin incorrigibilis "not to be corrected," from in- "not, opposite of" (see in- (1)) + corrigibilis, from corrigere "to correct" (see correct (v.)). From mid-15c. as "incapable of improvement" (of persons). Related: Incorrigibly. As a noun, from 1746.
incorruptibility (n.): mid-15c., from Late Latin incorruptibilitas, from incorruptibilis (see incorruptible).
incorruptible (adj.): mid-14c., in a physical sense, from Old French incorruptible (14c.), or directly from Late Latin incorruptibilis "incorruptible," from Latin incorruptus "unspoiled, unseduced," from in- "not" (see in- (1)) + corruptus (see corrupt (adj.)). From 1660s in English in a moral sense. Related: Incorruptibly.
increase (v.): mid-14c., encresen, "become greater in size or number" (intransitive); late 14c., "cause to grow, enlarge" (transitive), from Anglo-French encress-, Old French encreiss-, present participle stem of encreistre, from Latin increscere "to increase, to grow upon, grow over, swell, grow into," from in- "in" (see in- (2)) + crescere "to grow" (see crescent). Modern English restored the Latin spelling 16c. Related: Increased; increasing.
increase (n.): late 14c., "action of increasing; results of an increasing," from increase (v.) or from verbs formed from the noun in Old French or Anglo-French. The stress shifted from 18c. to distinguish it from the verb.
increasingly (adv.): late 14c., from increasing (see increase (v.)) + -ly (2).
incredible (adj.): early 15c., "unbelievable, surpassing belief as to what is possible," from Latin incredibilis "not to be believed, extraordinary," from in- "not" (see in- (1)) + credibilis "worthy of belief" (see credible). Used c. 1400 in a now-extinct sense of "unbelieving, incredulous." Related: Incredibly; incredibility.
incredulity (n.): "disbelieving frame of mind," early 15c., from Middle French incrédulité, from Latin incredulitatem (nominative incredulitas) "unbelief," noun of quality from incredulus "unbelieving" (see incredulous).
incredulous (adj.): "unbelieving," 1570s, from Latin incredulus "unbelieving, incredulous," from in- "not" (see in- (1)) + credulus (see credulous). Formerly also of religious beliefs. Related: Incredulously; incredulousness.
increment (n.): mid-15c., "act or process of increasing," from Latin incrementum "growth, increase; an addition," from stem of increscere "to grow in or upon" (see increase (v.)). Meaning "amount of increase" first attested 1630s.
incremental (adj.): 1715, from increment + -al (1). Related: Incrementally.
increpation (n.): "a chiding, a rebuking, censure," c. 1500, from Late Latin increpationem (nominative increpatio), noun of action from past participle stem of Latin increpare "to make noise at, scold, nag, upbraid," from in- "in" (see in- (2)) + crepare "to creak" (see raven (n.)).
incriminate (v.): 1730, back-formation from incrimination (q.v.) or else from Medieval Latin incriminatus, past participle of incriminare "to incriminate, accuse." Related: Incriminated; incriminating.
incrimination (n.): 1650s, noun of action from Medieval Latin incriminare "to incriminate, accuse," from in- "in" (see in- (2)) + criminare "to accuse of a crime," from crimen (genitive criminis) "crime" (see crime).
incriminatory (adj.): 1838; see incriminate + -ory.
incroyable (n.): 1796, from French incroyable, literally "incredible" (15c.), from in- "not, opposite of, without" (see in- (1)) + croire "to believe," from Latin credere (see credo). A name for the French fop or dandy of the period of the Directory (1795-99). Said to be so called from their extravagant dress, and also, according to OED, from a favorite expression among them ("C'est vraiment incroyable").
incrustation (n.): in early use also also encrustation, 1640s, from French encrustation, incrustation, from encruster (see encrust). Or perhaps from the obsolete English verb incrustate, which is attested from 1560s.
incubate (v.): 1640s (transitive), "to brood upon, watch jealously" (figurative); 1721 in literal sense "to sit on (eggs) to hatch them," from Latin incubatus, past participle of incubare "to lie in or upon," also in the figurative sense "brood" (see incubation). Intransitive sense "to sit upon eggs" is from 1755. Related: Incubated; incubating.
incubation (n.): 1610s, "a brooding," from Latin incubationem (nominative incubatio) "a laying upon eggs," noun of action from past participle stem of incubare "to hatch," literally "to lie on, rest on," from in- "on" (see in- (2)) + cubare "to lie" (see cubicle). The literal sense of "sitting on eggs to hatch them" in English is first recorded 1640s.
incubator (n.): "apparatus for hatching eggs by artificial heat," 1845, agent noun from incubate (v.). Late Latin incubator meant "one who lies in a place."
incubus (n.): "imaginary being or demon, credited with causing nightmares, and, in male form, consorting with women in their sleep," c. 1200, from Late Latin incubus (Augustine), from Latin incubo "nightmare, one who lies down on (the sleeper)," from incubare "to lie upon" (see incubate). Plural is incubi. Compare succubus.
inculcate (v.): 1540s, from Latin inculcatus, past participle of inculcare "force upon, insist; stamp in, impress, tread down," from in- "in" (see in- (2)) + calcare "to tread, press in," from calx (1) "heel" (see calcaneus). Related: Inculcated; inculcating.
inculcation (n.): 1550s, from inculcate (v.), or else Late Latin inculcationem (nominative inculcatio), noun of action from past participle stem of inculcare "to force upon; stamp in."
inculpable (adj.): late 15c., from Late Latin inculpabilis "unblamable," from in- "not, opposite of" (see in- (1)) + culpabilis (see culpable).
inculpate (v.): "to accuse, bring charges against," 1794, from Medieval Latin inculpatus, past participle of inculpare "to reproach, blame, censure," from Latin in- "in" (see in- (2)) + culpare "to blame," from culpa "fault." But inculpable (late 15c.) means "not culpable, free from blame," from Latin in- "not" (see in- (1)) + culpare.
inculpation (n.): "incrimination," 1798, noun of action from inculpate (v.). Perhaps from or modeled on French inculpation (18c.).
incumbency (n.): "state of being an incumbent," c. 1600, from incumbent + -cy.
incumbent (n.): early 15c., "person holding a church position," from Medieval Latin incumbentem (nominative incumbens) "holder of a church position," noun use of present participle of incumbere "to obtain or possess," from Latin incumbere "recline on," figuratively "apply oneself to," from in- "on" (see in- (2)) + -cumbere "lie down," related to cubare "to lie" (see cubicle). Extended to holders of any office from 1670s.
incumbent (adj.): 1560s, in relation to duties or obligations, from Medieval Latin incumbentem (nominative incumbens), present participle of incumbere (see incumbent (n.)). The literal, physical sense "lying or resting on something" is rare in English and first attested 1620s.
incumbrance (n.): see encumbrance.
incunabula (n.): "swaddling clothes," also, figuratively, "childhood, beginnings, place where a thing had its earliest development," 1824, from Latin incunabula (neuter plural) "a cradle; a birthplace," figuratively "rudiments or beginnings," from in- "in" (see in- (2)) + cunabula, diminutive of cunae "cradle," from PIE *koi-na-, from root *kei- "to lie; bed, couch" (see cemetery).
incunabulum (n.): 1861, singular of Latin incunabula "cradle, birthplace; rudiments or beginnings" (see incunabula); taken up (originally in German) as a word for any book printed late 15c., in the infancy of the printer's art.
incur (v.): c. 1400, "bring (an undesirable consequence) upon oneself;" mid-15c. as "become liable for (payment or expenses)," from Anglo-French encurir, Old French encorir "to run, flee; commit, contract, incur" (Modern French encourir), from Latin incurrere "run into or against, rush at, make an attack;" figuratively, "to befall, happen, occur to," from in- "upon" (see in- (2)) + currere "to run" (see current (adj.)). Related: Incurred; incurring.
incurable (adj.): mid-14c., from Old French incurable "not curable" (13c.), from Late Latin incurabilis "not curable," from in- "not" (see in- (1)) + curabilis "curable" (see curable). As a noun, "incurable person," from 1650s. Related: Incurably.
incurious (adj.): 1560s, "negligent, heedless," from Latin incuriosus "careless, negligent, unconcerned," from in- "not, opposite of, without" (see in- (1)) + curiosus (see curious). Meaning "uninquisitive" is from 1610s. Objective sense of "unworthy of attention" is from 1747. Related: Incuriously. Incuriosity is attested from c. 1600.
incursion (n.): "hostile attack," early 15c., from Old French incursion "invasion, attack, assault" (14c.) or directly from Latin incursionem (nominative incursio) "a running against, hostile attack," noun of action from past participle stem of incurrere "run into or against, rush at" (see incur).
incus (n.): middle ear bone, 1660s, from Latin incus "anvil," from incudere "to forge with a hammer," from in- "in" + cudere "to strike, beat," from PIE *kau-do-, suffixed form of root *kau- "to hew, strike" (see hew). The bone so called by Belgian anatomist Andreas Vesalius (1514-1564).
indear (v.): see endear.
indearing (adj.): see endearing.
indebted (adj.): late 14c., endetted "owing money, liable for borrowed money," past participle of endetten "to indebt, oblige," from Old French endeter "to involve in debt, run into debt," from en- "in" (see in- (2)) + dete "debt" (see debt). Figurative sense of "under obligation for favors or services" first attested 1560s. Spelling re-Latinized in English from 16c. The verb indebt is now rare or obsolete. Related: Indebtedness. Latin indebitus meant "not owed, not due."
indecency (n.): 1580s, "outrageous conduct," from Latin indecentia "unseemliness, impropriety," noun of quality from indecentem "unbecoming" (see indecent). Now especially of conduct which violates recognized standards of propriety (1690s).
indecent (adj.): 1560s, "unbecoming, in bad taste," from French indécent (14c.) or directly from Latin indecentem (nominative indecens) "unbecoming, unseemly," from in- "not, opposite of, without" (see in- (1)) + decens (see decent). Sense of "offending against propriety" is from 1610s. Indecent assault (1861) originally covered sexual assaults other than rape or intended rape, but by 1934 it was being used as a euphemism for "rape." Related: Indecently
indecipherable (adj.): 1802, from in- (1) "not" + decipherable (see decipher (v.)). Undecipherable is older. Related: Indecipherably; indecipherability.
indecision (n.): 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.