Online Etymology Dictionary

mitigation (n.): mid-14c., from Latin mitigationem (nominative mitigatio), noun of action from past participle stem of mitigare (see mitigate).
mitochondria (n.): 1901, from German, coined 1898 by microbiologist Carl Benda (1857-1933), from Greek mitos "thread" (see mitre) + khondrion "little granule," diminutive of khondros "granule, lump of salt" (see grind (v.)).
mitochondrion (n.): singular of mitochondria.
mitosis (n.): 1887, coined in German from Greek mitos "warp thread" (see mitre) + Modern Latin -osis "act, process." Term introduced by German anatomist Walther Fleming (1843-1905) in 1882. So called because chromatin of the cell nucleus appears as long threads in the first stages.
mitrailleuse (n.): kind of machine gun, from French mitrailleuse (19c.), from Old French mitaille (14c.) "small coins," hence "old iron, scrap iron," then "grapeshot;" originally a diminutive of mite "a small coin" (see mite (n.2)). "For sense development it should be borne in mind that orig. guns used to be loaded with scrap iron" [Klein].
mitral (adj.): c. 1600, "resembling a mitre," from French mitral, from Modern Latin mitralis, from Latin mitra (see mitre). Mitral valve is attested from 1705.
mitre (n.): bishop's tall hat, late 14c., from Old French mitre, from Latin mitra "headband, turban," from Greek mitra "headband, turban," earlier a belt or cloth worn under armor about the waist, from PIE root *mei- "to tie" (source also of Sanskrit Mitrah, Old Persian Mithra-, god names; Russian mir "world, peace," Greek mitos "a warp thread"). In Latin, "a kind of headdress common among Asiatics, the wearing of which by men was regarded in Rome as a mark of effeminacy" [OED]. But the word was used in Vulgate to translate Hebrew micnepheth "headdress of a priest."
mitt (n.): 1765, shortened form of mitten (q.v.). Baseball sense is from 1902. Slang sense of "hand" is from 1896.
mitten (n.): late 14c., from Old French mitaine "mitten, half-glove" (12c.), from Old French mite "mitten," and from Medieval Latin mitta, which are perhaps from Middle High German mittemo, Old High German mittamo "middle, midmost" (reflecting notion of "half-glove"), or from Vulgar Latin *medietana "divided in the middle," from Latin medius (see medial (adj.)).
Mitty: "adventurous daydreamer," 1950, from title character in "The Secret Life of Walter Mitty," short story by U.S. author James Thurber (1894-1961) first published in the "New Yorker" March 18, 1939.
mitzvah (n.): Jewish rabbinical commandment, 1640s, from Hebrew mitzwah "commandment, precept," from base of tziwwah "he commanded," related to Arabic wasa "he bound, united."
mix (v.): 1530s, back-formation from Middle English myxte (early 15c.) "composed of more than one element, of mixed nature," from Anglo-French mixte, from Latin mixtus, past participle of miscere "to mix, mingle, blend; fraternize with; throw into confusion," from PIE *meik- "to mix" (source also of Sanskrit misrah "mixed," Greek misgein, mignynai "to mix, mix up, mingle; to join, bring together; join (battle); make acquainted with," Old Church Slavonic mešo, mesiti "to mix," Russian meshat, Lithuanian maišau "to mix, mingle," Welsh mysgu). Also borrowed in Old English as miscian. Related: Mixed; mixing.
mix (n.): 1580s, "act of mixing," from mix (v.).
mix-up (n.): "confusion," 1841, from mix (v.) + up.
mixed (adj.): mid-15c., from mix (n.). Mixed blessing from 1933. Mixed marriage is from 1690s (originally in a religious context; racial sense was in use by 1942 in U.S., though mixed breed in reference to mulattoes is found by 1775). Mixed bag "heterogeneous collection" is from 1936. Mixed up is from 1884 as "confused," from 1862 as "involved."

Mixed drink in the modern liquor sense is recorded by 1868; the thing itself is older; Bartlett (1859) lists sixty names "given to the various compounds or mixtures of spirituous liquors and wines served up in fashionable bar rooms in the United States," all from a single advertisement. The list includes Tippe na Pecco, Moral suasion, Vox populi, Jewett's fancy, Ne plus ultra, Shambro, Virginia fancy, Stone wall, Smasher, Slingflip, Pig and whistle, Cocktail, Phlegm-cutter, Switchel flip, Tip and Ty, Ching-ching, Fiscal agent, Slip ticket, Epicure's punch.
mixer (n.): 1610s, "worker who mixes," agent noun from mix (v.). As a type of machine, from 1876. Meaning "troublemaker" attested by 1938; sense of "social gathering to mingle and get acquainted" dates from 1916.
mixo-: word-forming element meaning "mixed," from Greek mixo-, from mixis "a mixing, mingling, intercourse," from root of mignynai "to mix, mix up, mingle" (see mix (v.)). E.g. Mixolydian.
mixologist (n.): "bartender," 1856, jocular slang formation from mix (v.) + ending from the sciences.
mixture (n.): early 15c., from Old French misture and directly from Latin mixtura "a mixing," from mixtus (see mix (v.)).
miz: 1907 as graphing of U.S. Southern pronunciation of Mrs. or Miss; 1972 as standard pronunciation of Ms.
mizzen (n.): "aftermost fore-and-aft sail of a three-masted ship," early 15c., from Middle French misaine "foresail, foremast," altered (by influence of Italian mezzana "mizzen") from Old French migenne, from Catalan mitjana, from Latin medianus "of the middle" (see median). The sense in this transmission must have been something other than "middle," or the thing described changed, because the "middle" mast on a ship is the mainmast. Klein suggests an alternate etymology of the French word from Arabic, via Italian.
mnemonic (adj.): "aiding the memory," 1753, back-formation from mnemonics, or from Greek mnemonikos "of or pertaining to memory," from mnemon (genitive mnemonos) "remembering, mindful," from memne "memory, a remembrance, record, an epitaph; memory as a mental faculty," from base of mnasthai "remember," from PIE root *men- "to think" (see mind (n.)). The noun meaning "mnemonic device" is from 1858. Related: Mnemonical (1660s).
mnemonics (n.): "art of developing memory," 1721; see mnemonic; also see -ics.
Mnemosyne: titaness, mother of the Muses, from Greek mnemosyne, literally "memory, remembrance," from mneme "memory" (see mnemonic).
mnesic (adj.): "pertaining to memory," from Greek mnesikos "of memory," from mnesis "memory" (see mnemonic).
mnestic (adj.): "pertaining to memory," from Greek mnestis "remembrance," related to mnesis "memory" (see mnemonic) + -ic.
mo (1): colloquial shortening of momentum, by 1896.
mo (2): representing African-American vernacular pronunciation of more, by 1902; it was an acceptable variant form of more in the Middle Ages and has roots in Old English; see more.
moa (n.): extinct, flightless bird of New Zealand, 1842, native Maori name.
moan (n.): c. 1200, "lamentation, mourning, weeping; complaining, the expressing of complaints; a complaint; lover's complaint; accusation, charge," probably from an unrecorded Old English *man "complaint," related to Old English mænan "complain, moan," also "tell, intend, signify" (see mean (v.1)); but OED discounts this connection. Meaning "long, low inarticulate murmur from some prolonged pain" is first recorded 1670s, "with onomatopoeic suggestion" [OED].
moan (v.): mid-13c., "mourn (someone); regret, bewail;" c. 1300, "to lament, grieve; utter moans;" probably from Old English *manan, related to mænan "to lament" (see moan (n.)). From 1724 as "to make a low, mournful sound." Related: Moaned; moaning.
moat (n.): mid-14c., from Old French mote "mound, hillock, embankment; castle built on a hill" (12c.; Modern French motte), from Medieval Latin mota "mound, fortified height," of unknown origin, perhaps from Gaulish mutt, mutta. Sense shifted in Norman French from the castle mound to the ditch dug around it. As a verb, "to surround with a moat," early 15c.
mob (n.): 1680s, "disorderly part of the population, rabble," slang shortening of mobile, mobility "common people, populace, rabble" (1670s, probably with a conscious play on nobility), from Latin mobile vulgus "fickle common people" (the phrase attested c. 1600 in English), from mobile, neuter of mobilis "fickle, movable, mobile" (see mobile (adj.)). In Australia and New Zealand, used without disparagement for "a crowd." Meaning "gang of criminals working together" is from 1839, originally of thieves or pick-pockets; American English sense of "organized crime in general" is from 1927.
The Mob was not a synonym for the Mafia. It was an alliance of Jews, Italians, and a few Irishmen, some of them brilliant, who organized the supply, and often the production, of liquor during the thirteen years, ten months, and nineteen days of Prohibition. ... Their alliance -- sometimes called the Combination but never the Mafia -- was part of the urgent process of Americanizing crime. [Pete Hamill, "Why Sinatra Matters," 1998]
Mob scene "crowded place" first recorded 1922.
mob (v.): "to attack in a mob," 1709, from mob (n.). Meaning "to form into a mob" is from 1711. Related: Mobbed; mobbing.
mob-cap (n.): a type of woman's indoor cap, 1795 (as simply mob, 1748), from cap (n.) + obsolete mob (n.) "negligent attire" (1660s), earlier "a strumpet" (earlier form mab, 1550s), related to obsolete verb mob "to tousle the hair, to dress untidily" (1660s), and perhaps ultimately from mop, but influenced by Mab as a female name. Dutch has a similar compound, mopmuts, but the relationship between it and the English word is uncertain.
mobile (adj.): late 15c., from Middle French mobile (14c.), from Latin mobilis "movable, easy to move; loose, not firm," figuratively, "pliable, flexible, susceptible, nimble, quick; changeable, inconstant, fickle," contraction of *movibilis, from movere "to move" (see move (v.)). Sociology sense from 1927. Mobile home first recorded 1940.
Mobile: city in Alabama, U.S., attested c. 1540 in Spanish as Mauvila, referring to an Indian group and perhaps from Choctaw (Muskogean) moeli "to paddle." Related: Mobilian.
mobile (n.): early 15c. in astronomy, "outer sphere of the universe," from mobile (adj.); the artistic sense is first recorded 1949 as a shortening of mobile sculpture (1936). Now-obsolete sense of "the common people, the rabble" (1670s) led to mob (n.).
mobilisation (n.): chiefly British English spelling of mobilization. For spelling, see -ize.
mobilise (v.): chiefly British English spelling of mobilize; for suffix, see -ize. Related: Mobilised; mobilising.
mobility (n.): early 15c., "capacity for motion," from Old French mobilité "changeableness, inconsistency, fickleness," from Latin mobilitatem (nominative mobilitas) "activity, speed," figuratively "changeableness, fickleness, inconstancy," from mobilis (see mobile (adj.)). Socio-economics sense is from 1900 and writers in sociology.
mobilization (n.): 1799, "a rendering movable," from French mobilisation, from mobiliser (see mobilize). Military sense is from 1866.
mobilize (v.): 1833 in the military sense; 1838 as "render capable of movement, bring into circulation," from French mobiliser, from mobile "movable" (see mobile). Related: Mobilized; mobilizing.
Mobius: also Moebius, 1904 in reference to the Mobius strip (earlier Moebius unilateral paper strip, 1899), named for German mathematician August Ferdinand Möbius (1790-1868), professor at Leipzig, who devised it and described it in 1865 ("über die Bestimmung des Inhalts eines Polyeders", Nov. 27, 1865).
Mobius strip (n.): one-sided object, 1904, see Mobius.
mobocracy (n.): "mob rule," 1754, a hybrid from mob (n.) + -cracy. Related: Mobocrat; mobocratic.
mobster (n.): 1916, from mob (n.) in the criminal sense + -ster.
moccasin (n.): "North American Indian shoe" (made of deerskin or soft leather), 1610s, from an Algonquian language of Virginia, probably Powhatan makasin "shoe," from Central Atlantic Coast Algonquian *mockasin, similar to Southern New England Algonquian *makkusin, Munsee Delaware mahkusin, Ojibwa makizin. The venomous snake of southern U.S. (1784) is perhaps a different word, but Bright regards them as identical.
mocha (n.): 1733, "fine coffee," from Mocha, Red Sea port of Yemen, from which coffee was exported. Meaning "mixture of coffee and chocolate" first recorded 1849. As a shade of dark brown, it is attested from 1895.
mock (v.): mid-15c., mokken, "make fun of," also "to trick, delude, make a fool of, treat with scorn;" from Old French mocquer "deride, jeer," a word of unknown origin. Perhaps from Vulgar Latin *muccare "to blow the nose" (as a derisive gesture), from Latin mucus; or possibly from Middle Dutch mocken "to mumble" or Middle Low German mucken "grumble." Or perhaps simply imitative of such speech. Related: Mocked; mocking; mockingly. Replaced Old English bysmerian. Sense of "imitating," as in mockingbird and mock turtle (1763), is from notion of derisive imitation.