Online Etymology Dictionary

incase (v.): variant of encase.
Theory of Incasement, an old theory of reproduction which assumed that when the first animal of each species was created, the germs of all other individuals of the same species which were to come from it were incased in its ova. The discovery of spermatozoa developed the theory in two opposite directions: the ovulists, or ovists, held still to the theory of incasement in the female while the animalculists, or spermists, entertained the theory of incasement in the male. [Century Dictionary]
inaudibility (n.): 1808, from inaudible + -ity.
IPA (n.): also I.P.A., 1952, abbreviation of India pale ale.
incondite (adj.): 1630s, "ill-made," earlier "crude, upolished" (1530s), from Latin inconditus "disordered, uncouth," from in- "not, opposite of" (see in- (1)) + conditus, past participle of condere "put together" (see abscond). Applied from 1845 to natural utterances ("oh!") from Latin (vox) incondita.
inconsiderateness (n.): 1590s, "imprudence," from inconsiderate + -ness. From 1858 as "want of consideration for others."
inconsumable (adj.): 1640s in reference to fire; 1785 in political economy; from in- (1) "not" + consumable. Inconsumptible is from 1570s.
incontiguous (adj.): 1650s, from Late Latin incontiguus, from in- "not" (see in- (1)) + contiguus (see contiguous). Related: Incontiguously; incontiguousness.
inconsummate (adj.): "unfinished, incomplete," 1640s, from Late Latin inconsummatus "unfinished," from in- "not" (see in- (1) + consummatus "perfected, complete," past participle of consummare "sum up, to complete" (see consummation).
inconvertible (adj.): 1640s, from in- (1) "not, opposite of" + convertible (adj.). Related: Inconvertibly.
in-country (n.): "interior regions" of a land, 1560s, from in (prep.) + country.
inculpable (adj.): late 15c., from Late Latin inculpabilis "unblamable," from in- "not, opposite of" (see in- (1)) + culpabilis (see culpable).
indear (v.): see endear.
indearing (adj.): see endearing.
indeliberation (n.): 1610s; see in- (1) "not, opposite of" + deliberation.
indelicacy (n.): 1712, from indelicate + -cy.
indecorum (n.): 1570s, from Latin indecorum, noun use of neuter of adjective indecorus "unbecoming, unseemly, unsightly" (see indecorous).
indemonstrable (adj.): 1560s, from in- (1) "not, opposite of" + demonstrable.
indent (v.2): "to dent or press in," c. 1400, from in (adv.) + dent (v.). Etymologically distinct from indent (v.1) but felt as the same.
indent (n.): "cut or notch in a margin," 1590s, from indent (v.1). A supposed earlier noun sense of "a written agreement" (late 15c.) is described in Middle English Dictionary as "scribal abbrev. of endenture."
indentation (n.2): "action of making a dent or impression; small hollow or depression, slight pit," 1847, from indent (v.2).
indenture (v.): 1650s, "enter into a covenant;" 1670s, "bind by indenture," from indenture (n.). It was used earlier in a sense "to wrinkle, furrow" (1630s). Related: indentured; indenturing.
indetermination (n.): 1640s, from in- (1) "not, opposite of" + determination.
indeterminism (n.): 1874 in philosophy, from in- (1) "not, opposite of" + determinism.
indictable (adj.): mid-15c., enditable, "capable of being indicted, liable to indictment," from indict + -able. From 1721 of actions, "that may be punished by indictment."
indium (n.): metallic element, 1864, Modern Latin, from indicum "indigo" (see indigo) + chemical name element -ium. So called for its spectral lines. Ferdinand Reich (1799-1882), professor of physics at Freiberg, isolated it while analyzing local zinc ores in 1863 and identified it as a new element by the two dark blue lines in its spectrum, which did not correspond to any known element. The discovery had to be observed by his assistant, Theodor Richter, because Reich was color-blind.
individualization (n.): also individualisation, noun of action from individualize. Attested in 1746 but rare in English before 1820s, in which use probably it is a borrowing from French or German.
Indo-: word-forming element meaning "of or pertaining to India" (and some other place), from Greek Indo-, from Indos "India" (see India).
indocile (adj.): c. 1600, from French indocile (15c.) or directly from Latin indocilis, from in- "not, opposite of" (see in- (1)) + docilis (see docile).
Indo-Iranian (adj.): 1838, from Indo- + Iranian.
Indo-Pacific (adj.): 1851, in biology, from Indo- + Pacific.
Indo-Germanic (adj.): 1835, from German; see Indo-European.
Indra: Vedic thunder god, from Sanskrit Indrah, a word of uncertain origin.
indorse (v.): see endorse. Indorser was old slang for "a sodomite" (1785).
indubious (adj.): "certain, not doubtful," 1620s, from Latin indubius "not doubtful," from in- "not, opposite of" (see in- (1)) + dubius "vacillating, fluctuating," figuratively "wavering in opinion, doubting" (see dubious). Related: Indubiously.
indurate (adj.): "hardened, made hard," early 15c., from Latin induratus, past participle of indurare "to make hard, harden" (see endure).
indiscretionary (adj.): 1788, from indiscretion + -ary.
incohesion (n.): 1781; see in- (1) "not, opposite of" + cohesion.
incivilization (n.): "lack or loss of civilization," 1793; see in- (1) "not, opposite of" + civilization. Decivilization in the same sense is from 1815.
ineconomy (n.): "waste of resources," 1881, from in- (1) "not, opposite of" + economy (n.).
ineffectible (adj.): "that cannot be carried out, impracticable," 1803, from in- (1) "not, opposite of" + effectible (see effect (v.)).
inedita (n.): "unpublished writings," Modern Latin noun use of neuter plural of Latin ineditus, from in- "not, opposite of" (see in- (1)) + editus, past participle of edere "to bring forth, produce" (see edition).
ineffaceable (adj.): 1804, from in- "not, opposite of" (see in- (1)) + effaceable (see efface). Perhaps modeled on French ineffaçable (16c.).
inenarrable (adj.): "inexpressible, that cannot be told, indescribable," c. 1500, from Old French inenarrable (14c.) or directly from Latin inenarrabilis, from in- "not, opposite of" (see in- (1)) + enarrabilis "describable," from enarre "to narrate."
inefficiency (n.): 1749; see in- (1) "not, opposite of" + efficiency (n.).
hole-in-the-wall (n.): "small and unpretentious place," 1816, perhaps recalling the hole in the wall that was a public house name in England from at least 1690s. "Generally it is believed to refer to some snug corner, perhaps near the town walls," but the common story was that it referred to "the hole made in the wall of the debtors' or other prisons, through which the poor prisoners received the money, broken meat, or other donations of the charitably inclined" [Jacob Larwood and John Camden Hotten, "The History of Signboards: From the Earliest Times to the Present Day," 1867]. Mid-19c. it was the name of the private liquor bar attached to the U.S. Congress.
Islamist (n.): 1850, "a Muslim," from Islam + -ist. Later also "scholar of Islamic studies." By 1962 specifically as "strict fundamentalist Sunni Muslim." Islamism is attested from 1747 as "the religion of the Muslims, Islam." Islamite "a Muslim" is from 1786 (1768 as an adjective); Islamize/Islamise (v.) is from 1849.
-ing (3): Old English -ing, patronymic suffix (denoting common origin); surviving in place names (Birmingham, Nottingham) where it denotes "tribe, community."
ism (n.): "distinctive doctrine, theory, or practice," 1670s, the suffix -ism used as an independent word, chiefly disparagingly. Related: Ismatical. By the same path, ist is from 1811.
ichthyo-: word-forming element meaning "fish," from Latinized form of Greek ikhthys "a fish" (in plural, "a fish-market"), from PIE root *dhghu- "fish" (source also of Armenian jukn, Lithuanian žuvis).
ichthyomorphic (adj.): "fish-shaped," 1870 in biology, 1879 in mythology, from icthyo- "fish" + -morphic, from Greek morphe "form, shape" (see Morpheus).