Online Etymology Dictionary

ichthyophagous (adj.): "fish-eating," 1791, from Latinized form of ikhthyophagos "fish-eating;" see ichthyo- + -phagous. Related: Ichthyophagist (1727).
ichnomancy (n.): "the reading of traces of footsteps to determine the nature and peculiarities of what made them," 1855, from Latinized form of Greek ikhnos "a track, footprint" + -mancy.
Iapetus: a titan, son of Uranus and Gaia.
ice-cube (n.): 1904, from ice (n.) + cube (n.).
ice-bound (adj.): 1650s, from ice (n.) + bound (adj.1).
ice-pick (n.): 1858, from ice (n.) + pick (n.1).
ice-cap (n.): 1859 in geology, from ice (n.) + an extended sense of cap (n.).
ice-chest (n.): 1839, originally a wooden chest lined with zinc, from ice (n.) + chest (n.).
ice-house (n.): 1680s, from ice (n.) + house (n.).
Iceland: c. 1200, so called for its ice-choked fjords. Related: Icelander; Icelandic.
ickle (adj.): childish pronunciation of little (adj.), attested by 1846.
iconology (n.): "study of icons," 1736; see icon + -logy.
ide (n.): see ides.
ideality (n.): 1817, "quality of being ideal;" see ideal (adj.) + -ity. In phrenology, "imaginative faculty" (1828); as the opposite of reality, 1877.
ideo-: word-forming element variously used with reference to images or to ideas, from Greek idea (see idea).
idiolatry (n.): "self-worship," 1620s, from idio- "self" + -latry "worship." Related: Idiolater; idiolatrous.
idioticon (n.): "a dictionary of a dialect," 1842, via German, from Latinized form of idiotikon, neuter of Greek idiotikos, from idioma (see idiom).
idiotype (n.): "object typical of a class," 1865; see idio- "distinct" + type (n.). Related: Idiotypic.
idolization (n.): 1773, noun of action from idolize.
Idumaean (adj.): in reference to the biblical Edom, from Latin Idumaea "Edom," from Greek Idoumaia, from Hebrew Edom.
igneo-: word-forming element meaning "of fire; of fire and; of igneous origin," from Latin igneus (see igneous).
Ilium: "Troy;" see Iliad.
ill-advised (adj.): 1590s, from ill (adv.) + advise (v.). Related: Ill-advisedly.
ill-bred (adj.): 1620s, from ill (adv.) + bred (adj.).
ill-fated (adj.): 1710 (Pope), from ill (adv.) + fated.
intra-ovarian (adj.): 1845; see intra- + ovarian.
incriminatory (adj.): 1838; see incriminate + -ory.
incensation (n.): "action of perfuming," 1851, noun of action from incense (v.2).
Inga: fem. proper name, usually a shortening of Ingrid (q.v.).
Ingrid: fem. proper name, Scandinavian or German, from Ing, Germanic god-name (Old Norse Yngvi, Old English Ingwine), apparently an earlier name of Freyr. He was associated with prosperity, virility, and fertility. Second element in the name is either friðr "fair, beautiful" or rida "to ride." As a given name for girls in the U.S., almost unknown before 1940 (about the time Swedish actress Ingrid Bergman rose to fame in Hollywood); it was most popular in 1960s and early '70s but never common.
know-it-all (n.): "one deemed (over)full of information or correct answers," 1895, from verbal phrase; see know (v.). Earlier in the same sense was know-all (1862); and Mr. Know-All was a minor character in Bunyan's "The Holy War" (1682).
lead-in (n.): 1913, in electrical wiring, from verbal phrase; see lead (v.1) + in (adv.). General sense of "introduction, opening" is from 1928, originally in music.
-ium: word-forming element in chemistry, used to coin element names, from Latin adjectival suffix -ium (neuter of -ius), which formed metal names in Latin (ferrum "iron," aurum "gold," etc.). In late 18c chemists began to pay attention to the naming of their substances with words that indicate their chemical properties. Berzelius in 1811 proposed forming all element names in Modern Latin. As the names of some recently discovered metallic elements already were in Latin form (uranium, chromium, borium, etc.), the pattern of naming metallic elements in -ium or -um was maintained (in cadmium, lithium, plutonium, etc.; helium is an anomaly).
initialism (n.): "written word formed from the first letters, in order, of other words in a name or phrase," 1957, from initial (n.) + -ism. The word was used earlier in a sense "group of initial letters of an author's name (rather than the full name) on a publication" (1868). An earlier term for what we now call an initialism was alphabetic abbreviation (1907).

The distinction from acronym is not universally agreed-upon; but in general, cases such as NATO, where the letters always are sounded as a word, are regarded as acronyms, those such as FBI, where the letters sound as letters, are initial-words or initialisms. The use of acronym in entries in this dictionary that are technically initialisms is a deliberate error, because many people will search all such words using "acronym."
in custodia legis (adv.): legal Latin, "in the custody of the law," from ablative of custodia "a guarding, watching, keeping" (see custody) + legis, genitive of lex "law" (see legal (adj.)).
infant (n.): late 14c., infant, infaunt, "a child," also especially "child during earliest period of life, a newborn" (sometimes meaning a fetus), from Latin infantem (nominative infans) "young child, babe in arms," noun use of adjective meaning "not able to speak," from in- "not, opposite of" (see in- (1)) + fans, present participle of fari "to speak," from PIE root *bha- (2) "to speak, tell, say" (see fame (n.)). As an adjective in English, 1580s, from the noun.

The Romans extended the sense of Latin infans to include older children, hence French enfant "child," Italian fanciullo, fanciulla. In English the word formerly also had the wider sense of "child" (commonly reckoned as up to age 7). The common Germanic words for "child" (represented in English by bairn and child) also are sense extensions of words that originally must have meant "newborn."
imprimatur (n.): "licence to print, granted by a licenser of the press," 1640, Modern Latin, literally "let it be printed," the formula of a book licenser, third person singular present subjunctive passive of Latin imprimere "to print, engrave, stamp; press upon, press against" (see impress (v.1)). Originally of state licence to print books, later only of Roman Catholic Church.
interlope (v.): "intrude where one has no business," especially with a view to gain the advantage or profits of another (as a trader without a proper licence), early 17c., probably a back-formation from interloper (q.v.). Related: Interloped; interloping.
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).
-ish: adjectival word-forming element, Old English -isc "of the nativity or country of," in later use "of the nature or character of," from Proto-Germanic suffix *-iska- (cognates: Old Saxon -isk, Old Frisian -sk, Old Norse -iskr, Swedish and Danish -sk, Dutch -sch, Old High German -isc, German -isch, Gothic -isks), cognate with Greek diminutive suffix -iskos. In its oldest forms with altered stem vowel (French, Welsh). The Germanic suffix was borrowed into Italian and Spanish (-esco) and French (-esque). Colloquially attached to hours to denote approximation, 1916.

The -ish in verbs (abolish, establish, finish, punish, etc.) is a mere terminal relic from the Old French present participle.
lived-in (adj.): "inhabited, occupied" (sometimes with suggestion of "shabby, disorderly"), 1873, from verbal phrase; see live (v.) + in (adv.).
live-in (adj.): "residing on the premises," 1950, from live (v.) + in (adv.). To live out was formerly "be away from home in domestic service."
-age: word-forming element in nouns of act, process, function, condition, from Old French and French -age, from Late Latin -aticum "belonging to, related to," originally neuter adjectival suffix, from PIE *-at- (source of Latin -atus, past participle suffix of verbs of the first conjugation) + *-(i)ko-, secondary suffix forming adjectives (see -ic).
mind (v.): mid-14c., "to remember, take care to remember," also "to remind," from mind (n.). Meaning "perceive, notice" is from late 15c.; that of "to give heed to" is from 1550s; that of "be careful about" is from 1737. Sense of "object to, dislike" is from c. 1600; negative use (with not) "to care for, to trouble oneself with" is attested from c. 1600. Meaning "to take care of, look after" is from 1690s. Related: Minded; minding. Meiotic expression don't mind if I do attested from 1847.
wist (v.): "to know" (archaic), c. 1500, from Old English past tense of witan "to know" (cognate with German wusste, past tense of wissen "to know"); see wit. Had-I-wiste was used c. 1400-1550 in sense "regret for something done rashly or heedlessly;" see wist. Proverbial in expression Had-I-wiste cometh ever too late.
Haddywyst comyth euer to late Whan lewyd woordis beth owte y-spronge. ["Commonplace book" in Trinity College, Cambridge, c. 1500]
AIDS (n.): 1982, acronym formed from acquired immune deficiency syndrome. AIDS cocktail attested by 1997, the thing itself said to have been in use from 1995.
Urdu: official language of Pakistan, 1796, formerly also known as Hindustani, from Urdu urdu "camp," from Turkish ordu (source of horde); short for zaban-i-urdu "language of the camp." Compare Dzongkha, a variant of Tibetan and the official language of Bhutan, literally "the language of the fortress." A form of Hindu heavily leavened with Persian and Arabic. "So named because it grew up since the eleventh century in the camps of the Mohammedan conquerors of India as a means of communication between them and the subject population of central Hindustan." [Century Dictionary]
Ottoman: 1580s (n.), c. 1600 (adj.), from French Ottoman, from Italian Ottomano, from Arabic 'Uthmani "of or belonging to 'Uthman," Arabic masc. proper name, which in Turkish is pronounced Othman (see Osmanli), name of the founder of the dynasty and empire. Ending altered in Italian by formation of a new false singular, because -i was a plural inflection in Italian. Byron used the more correct form Othman, and a few writers have followed him. The type of couch so called (1806) because one reclined on it, which was associated with Eastern customs (see couch).
divan (n.): 1580s, "Oriental council of state," from Turkish divan, from Arabic diwan, from Persian devan "bundle of written sheets, small book, collection of poems" (as in the "Divan i-Hafiz"), related to debir "writer."

Sense evolved through "book of accounts," to "office of accounts," "custom house," "council chamber," then to "long, cushioned seat," such as are found along the walls in Middle Eastern council chambers (see couch). The sofa/couch sense was taken into English 1702; the "book of poems" sense in 1823.
sentence (n.): c. 1200, "doctrine, authoritative teaching; an authoritative pronouncement," from Old French sentence "judgment, decision; meaning; aphorism, maxim; statement of authority" (12c.) and directly from Latin sententia "thought, way of thinking, opinion; judgment, decision," also "a thought expressed; aphorism, saying," from sentientem, present participle of sentire "be of opinion, feel, perceive" (see sense (n.)). Loss of first -i- in Latin by dissimilation.

From early 14c. as "judgment rendered by God, or by one in authority; a verdict, decision in court;" from late 14c. as "understanding, wisdom; edifying subject matter." From late 14c. as "subject matter or content of a letter, book, speech, etc.," also in reference to a passage in a written work. Sense of "grammatically complete statement" is attested from mid-15c. "Meaning," then "meaning expressed in words." Related: Sentential.