Online Etymology Dictionary

iterate (v.): 1530s, "to do again, repeat," back-formation from iteration, or else from Latin iteratus, past participle of iterare "do again, repeat." Related: Iterated; iterating.
iteration (n.): late 15c., from Latin iterationem (nominative iteratio) "a repetition," noun of action from past participle stem of iterare "do again, repeat," from iterum "again," from PIE *i-tero-, from pronominal root *i- (see yon).
iterative (adj.): "involving repetition," late 15c., from French iteratif (c. 1400), from Late Latin iterativus, from iterat-, past participle stem of Latin iterare "do again, repeat" (see iteration). As a noun, "an iterative word," by 1839. Related: Iteratively.
Ithaca: western Greek Island, legendary home of Odysseus; the first element is perhaps Phoenician i "island;" the rest is unknown. Related: Ithacan.
ither (adj., pron.): Scottish dialectal form of other.
Ithuriel's spear: the image is from "Paradise Lost," and turns up in late 19c. literature. The weapon caused anything it touched to assume its true form. Ithuriel is an archangel in the poem. The name is older and appears to be Kabbalistic.
ithyphallic (adj.): 1795, in reference to a type of meter used in ancient Greek poetry (earlier as a noun, "poem in ithyphallic meter," 1610s), from Latin ithyphallicus, from Greek ithyphallikos, from ithyphallos "phallus carried in the festivals," from ithys "straight, straight upward" + phallos "erect penis" (see phallus). Credited to Archilochus, the meter was that of the Bacchic hymns, which were sung in the rites during which such phalluses were carried. Thus, in Victorian times, the word also meant "grossly indecent" (1864) and sometimes was used in scholarly works in its literal sense of "with erect penis" (1837).
itinerant (adj.): 1560s (attested in Anglo-Latin from late 13c.), from Late Latin itinerantem (nominative itinerans), present participle of itinerare "to travel," from Latin iter (genitive itineris) "a journey," from ire "go" (see ion). Originally in reference to circuit courts. As a noun from 1640s. Related: Itinerancy. Middle English had itineral "having to do with travel" (late 15c.).
itinerary (n.): mid-15c., "route of travel," from Late Latin itinerarium "account of a journey, description of a route of travel, road-book," noun use of neuter of itinerarius "of a journey," from Latin itineris "a journey," from ire "go" (see ion). By early 15c. it meant "record of a journey;" extended sense "sketch of a proposed route, list of places to be included in a journey" is from 1856.
itinerate (v.): "to travel from place to place," c. 1600, from Late Latin itineratus, past participle of itinerare "to travel" (see itinerant). Especially "to travel from place to place preaching" (1775). Related: Itinerated; itinerating.
its (pron.): neuter possessive pronoun; late 16c., from it + genitive/possessive ending 's (q.v.). "[A]t first commonly written it's, a spelling retained by some to the beginning of the 19c." [OED]. The apostrophe came to be omitted, perhaps because it's already was established as a contraction of it is, or by general habit of omitting apostrophes in personal pronouns (hers, yours, theirs, etc.).

The neuter genitive pronoun in Middle English was his, but the clash between grammatical gender and sexual gender, or else the application of the word to both human and non-human subjects, evidently made users uncomfortable. Restriction of his to the masculine and avoidance of it as a neuter pronoun is evidenced in Middle English, and of it and thereof (as in KJV) were used for the neuter possessive. In literary use, his as a neuter pronoun continued into the 17c. In Middle English, simple it sometimes was used as a neuter possessive pronoun (c. 1300).
itself (pron.): late 14c., from Old English hit sylf, from it + self. Since 17c. usually regarded as its self (thus its own self, etc.).
itsy-bitsy (adj.): "charmingly small," 1890, from itty (baby-talk form of little) and/or bitsy. Bitsy-itsy is recorded from 1875. Itty-bitty from 1855; tiddy-itty from 1852.
The fond old captain used to talk of her very much as if she were six months old, and fractions in teething, calling her his Peetums-keetums, his Pitsy-itsy-kitsy and such like, which annoyed the girl, .... ["M.B.," "John's Wife," in "Tales of the Day," 1861]
itty (adj.): 1798, in a letter of Jane Austen, baby-talk form of little (adj.). Compare itsy-bitsy.
Ivan: masc. proper name, from Russian, literally "John," from Greek Ioannes (see John). As the personification of Russia, or the typical name for a Russian man (originally a Russian soldier), attested from 1870 (Ivanovitch).
ivied (adj.): 1771, from ivy (n.).
ivory (n.): mid-13c. (late 12c. as a surname), Anglo-French ivorie, from Old North French ivurie (12c.), from Medieval Latin eborium "ivory," noun use of neuter of Latin eboreus "of ivory," from ebur (genitive eboris) "ivory," probably via Phoenician from an African source (compare Egyptian ab "elephant," Coptic ebu "ivory").

It replaced Old English elpendban, literally "elephant bone." Applied in slang to articles made from it, such as dice (1830) and piano keys (1818). As a color, especially in reference to human skin, it is attested from 1580s. Ivories as slang for "teeth" dates from 1782. Black ivory was ivory burnt and powdered, used as a pigment (1810); the sense "African slaves as an article of commerce" is attested from 1834.
Mr. Dunlap then asked the witness what he himself traded in, when on the African coast, and he replied "sometimes in black ivory;" but, being more closely pressed to explain what he meant by "black ivory," he admitted that when he could not get a cargo of real ivory, he took one of slaves. ["Trial of the Twelve Spanish Pirates," Boston, 1834]
Related: Ivoried; ivorine.
ivory tower (n.): symbol of artistic or intellectual aloofness, by 1889, from French tour d'ivoire, used in 1837 by critic Charles-Augustin Sainte-Beuve (1804-1869) with reference to the poet Alfred de Vigny (1797-1863), whom he accused of excessive aloofness.
Et Vigny, plus secret, comme en sa tour d'ivoire, avant midi rentrait. [Sainte-Beuve, "Pensées d'Août, à M. Villemain," 1837]
Used earlier as a type of a wonder or a symbol of "the ideal." The literal image is perhaps from Song of Solomon [vii:4]:
Thy neck is as a tower of ivory; thine eyes like the fishpools in Heshbon, by the gate of Bathrabbim: thy nose is as the tower of Lebanon which looketh toward Damascus. [KJV]
ivy (n.): climbing plant, Old English ifig, from West Germanic *ibakhs (source also of Middle Low German iflof, Dutch eiloof, Old High German ebahewi, German Efeu), a word of unknown origin; the second element in the Old High German word might be heu "hay."

Ivy bush as a sign of a tavern where wine is served is attested from mid-15c. (the ivy being sacred to Bacchus). Ivy League, inspired by the image of old, ivy-mantled walls, dates to 1935, originally in reference to a conference of football teams agreeing to organize teams and play games by set rules; it consists of Brown, Columbia, Cornell, Dartmouth, Harvard, Pennsylvania, Princeton, and Yale.
Incidentally, "Ivy League" is a poor name; it suggests that athletic morality is concentrated in a few very old colleges. Obviously, membership should be determined not by the amount of ivy on an institution's walls, but by its willingness to adopt and follow certain fundamental principles of education and sport. ["Princeton Alumni Weekly," Dec. 6, 1935]
ixnay: "no, no more," pig Latin for nix (v.).
izard (n.): chamois-like antelope of the Pyrenees, 1791, from French isard, Gascon isart, "perhaps of Iberian origin" (according to French sources), or [Klein] from Basque (which has izzara "star").
Izod: clothing manufacturer trendy in the 1970s and 1980s, the company name was bought in 1930s from A.J. Izod, a London tailoring establishment. The surname (also Izzard, etc.) goes back to the Middle Ages and might be related to the proper name Isolt.
izzard (n.): old name for "Z," 1738, a variant of zed. The guess that it representes S-hard wants evidence.