Online Etymology Dictionary

Ojibwa: Algonquian people of North America living along the shores of Lake Superior, 1700, from Ojibwa O'chepe'wag "plaited shoes," in reference to their puckered moccasins, which were unlike those of neighboring tribes. The older form in English is Chippewa, which is usually retained in U.S., but since c. 1850 Canadian English has taken up the more phonetically correct Ojibwa, and as a result the two forms of the word have begun to be used in reference to slightly differing groups in the two countries. Some modern Chippewas prefer anishinaabe, which means "original people."
OK: 1839, only survivor of a slang fad in Boston and New York c. 1838-9 for abbreviations of common phrases with deliberate, jocular misspellings (such as K.G. for "no go," as if spelled "know go;" N.C. for "'nuff ced;" K.Y. for "know yuse"). In the case of O.K., the abbreviation is of "oll korrect."

Probably further popularized by use as an election slogan by the O.K. Club, New York boosters of Democratic president Martin Van Buren's 1840 re-election bid, in allusion to his nickname Old Kinderhook, from his birth in the N.Y. village of Kinderhook. Van Buren lost, the word stuck, in part because it filled a need for a quick way to write an approval on a document, bill, etc. Spelled out as okeh, 1919, by Woodrow Wilson, on assumption that it represented Choctaw okeh "it is so" (a theory which lacks historical documentation); this was ousted quickly by okay after the appearance of that form in 1929. Greek immigrants to America who returned home early 20c. having picked up U.S. speech mannerisms were known in Greece as okay-boys, among other things.

The noun is first attested 1841; the verb 1888. Okey-doke is student slang first attested 1932.
okapi (n.): short-necked giraffe of central Africa, 1900, from the animal's name in Mbuba (Congo). Reported by English explorer Sir Harry Johnston (1858-1927).
okay: see OK.
oke: slang clipping of OK, attested from 1929.
Okie: "migrant agricultural worker," especially one driven from farms in Oklahoma during the Dust Bowl, 1938, short for U.S. state of Oklahoma.
"Okie use' ta mean you was from Oklahoma. Now it means you're a dirty son-of-a-bitch." [John Steinbeck, "The Grapes of Wrath," 1939]
Okinawa: largest of the Ryuku island chain, Japanese, literally "rope on the sea." Related: Okinawan.
Oklahoma: from Choctaw, literally "red people," from okla "nation, people" + homma "red." Coined by Choctaw scholar Allen Wright, later principal chief of the Choctaw Nation, and first used in the Choctaw-Chickasaw treaty of April 28, 1866. Organized as a U.S. territory 1889; admitted as a state 1907. Related: Oklahoman.
okra (n.): 1670s, from a West African language (compare Akan nkruma "okra").
Olaf: masc. proper name, from Old Norse An-leifr, literally "ancestor's relic;" first element related to Old High German ano "ancestor;" second element related to Old English læfan "to leave" (see leave (v.)).
Olbers' paradox: "if stars are uniformly distributed through the sky, their number should counterbalance their faintness and the night sky should be as bright as the day;" named for German astronomer H.W.M. Olbers (1758-1840), who propounded it in 1826.
old (adj.): Old English ald (Anglian), eald (West Saxon) "aged, antique, primeval; elder, experienced," from Proto-Germanic *althaz "grown up, adult" (source also of Old Frisian ald, Gothic alþeis, Dutch oud, German alt), originally a past participle stem of a verb meaning "grow, nourish" (compare Gothic alan "to grow up," Old Norse ala "to nourish"), from PIE root *al- (3) "to grow, nourish" (source also of Greek aldaino "make grow, strengthen," althein, althainein "to get well;" Latin alere "to feed, nourish, bring up, increase," altus "high," literally "grown tall," almus "nurturing, nourishing," alumnus "fosterling, step-child;" Old Irish alim "I nourish").

The usual PIE root is *sen- (see senior (adj.)). A few Indo-European languages distinguish words for "old" (vs. young) from words for "old" (vs. new), and some have separate words for aged persons as opposed to old things. Latin senex was used of aged living things, mostly persons, while vetus (literally "having many years") was used of inanimate things. Greek geraios was used mostly of humans; Greek palaios was used mostly of things, of persons only in a derogatory sense. Greek also had arkhaios, literally "belonging to the beginning," which parallels French ancien, used mostly with reference to things "of former times."

Old English also had fyrn "ancient," related to Old English feor "far, distant" (see far, and compare Gothic fairneis, Old Norse forn "old, of old, of former times," Old High German firni "old, experienced"). The original Old English vowel is preserved in Scots auld, also in alderman. The original comparative and superlative (elder, eldest) are retained in particular uses.

First record of old-timer is from 1860. Expression old as the hills first recorded 1819. The good old days dates from 1828. Of old "of old times" is from late 14c. Old maid "woman who remains single well beyond the usual marrying age" is from 1520s; the card game is attested by that name from 1844. Old man "man who has lived long" is from c. 1200; sense of "husband, father, boss" is from 1854, earlier (1830) it was military slang for "commanding officer;" old lady "wife, mother" is attested from c. 1775 (but compare Old English seo ealde hlæfdige "the queen dowager"). Old English is attested from 1701, originally as a type of font. Old boy originally was a former pupil of one of the English public schools. Old Testament attested from mid-14c.
old hat (adj.): "out of date," first recorded 1911. As a noun phrase, however, it had different sense previously. The "Classical Dictionary of the Vulgar Tongue" (1796) defines it as, "a woman's privities, because frequently felt."
Old World (adj.): of or pertaining to Eurasia and Africa, as opposed to the Americas, 1877.
old-fashioned (adj.): 1590s, "in an outdated style," from old + past participle of fashion (v.). As a type of cocktail, attested from 1901, American English.
Old Fashioned Tom Gin Cocktail Mix same as Holland Gin Old Fashioned Cocktail using Old Tom gin in place of Holland [George J. Kappeler, "Modern American Drinks," Akron, Ohio, 1900]
old-school (adj.): in reference to a group of people noted for conservative views or principles on some professional or political matter, 1749, from old + school (n.).
old-time (adj.): 1824, from old + time (n.). Related: Old-timey (1850).
olde: pseudo-archaic mock-antique variant of old, 1927.
olden (adj.): early 15c., from old + -en (2).
oldie (n.): "an old person," 1874; "an old tune or film," 1940, from old + -ie. Related: Oldies, which is attested by 1961 as a radio format.
oldness (n.): Old English ealdnysse; see old + -ness.
oldster (n.): 1818, colloquial, from old + -ster, on analogy of youngster.
ole: 1922, from Spanish olé "bravo!"
oleaginous (adj.): 1630s, from French oléagineux (14c.), from Latin oleaginus "of the olive," from olea "olive," alteration of oliva (see olive) by influence of oleum "oil."
oleander (n.): "rose bay," a poisonous evergreen Mediterranean shrub, c. 1400, from Medieval Latin oleander, probably (by influence of Latin olea "olive tree") from Late Latin lorandrum, from Latin rhododendron (see rhododendron), itself altered by influence of Latin laurea "laurel," on resemblance of leaves. This round-about etymology is supported by the French word for it, laurier rose.
Oleg: masc. proper name; see Olga.
oleo (n.): 1884, commercial shortening of oleomargarine.
oleo-: word-forming element meaning "oil" or "oleic," from Latin oleum (see oil (n.)).
oleomargarine (n.): 1873, "butter substitute made from beef fat," from French oléomargarine (1854), from oléine (from Latin oleum "oil" + -ine, after glycerine) + margarine. It was regarded as a chemical compound of olein and margarine.
olfaction (n.): noun of action from Latin olfactus, past participle of olfacere "to smell, get the smell of" (transitive), from olere "to emit a smell" (see odor) + facere "to make" (see factitious).
olfactory (adj.): 1650s, from Latin olfactorius, from olfact-, past participle stem of olfacere "to get the smell of, sniff," from olere "emit a smell, give off a smell of" (see odor) + facere "to make" (see factitious).
Olga: fem. proper name, from Russian, probably from Norse Helga, literally "holy," from Proto-Germanic *hailaga, from PIE *kailo- (see health). The masc. form is Oleg.
oligarch (n.): c. 1600, from Middle French olygarche, oligarque, from Greek oligarkhes, related to oligarkhia (see oligarchy).
oligarchic (adj.): 1640s, from Greek oligarkhikos, from oligarkhos, related to oligarkhia (see oligarchy). Related: Oligarchical.
oligarchy (n.): 1570s, from Middle French oligarchie (14c.), from Greek oligarkhia "government by the few," from stem of oligos "few, small, little" (see oligo-) + arkhein "to rule" (see archon).
oligo-: before vowels olig-, word-forming element meaning "few, the few," from comb. form of Greek oligos "few, scanty, small, little," in plural, "the few;" of uncertain origin.
Oligocene (adj.): 1856, "pertaining to the Tertiary period between the Eocene and the Miocene," coined in German (1854) by Heinrich Ernst von Beyrich, from oligo- "small, little, few" + -cene. So called because few modern fossils were found in Oligocene rocks.
oligopolistic (adj.): 1939, from oligo- "little, small," in plural, "few" + -poly, from Greek polein "to sell" (see monopoly).
oligopoly (n.): 1887, from Medieval Latin oligopolium, from Greek oligos "little, small," in plural, "the few" (see oligo-) + polein "to sell" (see monopoly).
oligotrophy (n.): 1928, from oligo- "small, little" + -trophy "food, nourishment." Related: Oligotrophic.
oliguria (n.): 1843, from oligo- "small, little," + -uria, from Greek ouron "urine" (see urine).
olio (n.): medley dish of Iberian origin, 1640s, from Spanish olla, Portuguese olha, both from Vulgar Latin olla "pot, jar." Sense transferred to "any mixture or medley."
oliphant (n.): obsolete form of elephant, c. 1200; also used in Middle English with sense "ivory horn."
olive (n.): c. 1200, "olive tree," from Old French olive "olive, olive tree" (13c.) or directly from Latin oliva "olive, olive tree," from Greek elaia "olive tree, olive," probably from the same Aegean language (perhaps Cretan) as Armenian ewi "oil." Applied to the fruit or berry of the tree in English from late 14c. As a color from 17c. Olive branch as a token of peace is from early 13c.
Oliver: masc. personal name, in medieval lore the name of one of Charlemagne's peers, friend of Roland, from French Olivier, from Middle Low German Alfihar, literally "elf-host, elf-army," from alf "elf" (see elf) + hari "host, army" (see harry (v.)). Cognate with Anglo-Saxon name Ælfhere. Form influenced in Old French by olivier "olive tree."
Olivetti: brand of typewriters manufactured by company founded in 1908 near Turin, Italy; named for founder, Camillo Olivetti.
Olivia: fem. proper name, from Italian Olivia, from Latin oliva "olive" (see olive).
Olmec: ancient people and civilization of Mexico, 1787, from Nahuatl (Aztecan) Olmecatl (plural Olmeca), literally "inhabitant of the rubber country."
Olympiad (n.): late 14c., "period of four years" (between Olympic games), from Old French olimpiade "period of four years," from Latin Olympiadem, from Greek olympiados, genitive of Olympias (see Olympic). Used by ancient Greeks as a unit in computing time. Revived in modern usage with revival of the games, 1896.
Olympian (adj.): "of or belonging to Olympus," c. 1600; see Olympic + -ian. The noun meaning "a great god of ancient Greece" is attested from 1843, from Late Latin Olympianus, from Greek Olympios "pertaining to Olympus;" sense of "one who competes in the (modern) Olympic Games" is from 1976.