Online Etymology Dictionary

muted (adj.): 1861, in reference to musical instruments, past participle adjective from mute (v.). Figuratively by 1879. Of colors by 1939. Related: mutedness.
mutely (adv.): 1620s, from mute (adj.) + -ly (2).
muteness (n.): 1580s, from mute (adj.) + -ness.
mutilate (v.): 1530s, of things; 1560s, of persons; from Latin mutilatus, past participle of mutilare "to cut off, lop off, cut short; maim, mutilate," from mutilus "maimed" (see mutilation). Technically, to deprive of some principal part, especially by cutting off. Related: Mutilated; mutilating.
mutilation (n.): 1520s, in Scots law, "act of disabling or wounding a limb," from Middle French mutilation and directly from Late Latin mutilationem (nominative mutilatio), noun of action from past participle stem of Latin mutilare "to cut or lop off," from mutilus "maimed," which perhaps is cognate with Greek mytilos "hornless." Of things, "a destroying of unity by damaging or removing a part," from 1630s.
mutineer (n.): "one guilty of mutiny," c. 1600, from French mutinier (16c.), from Middle French meutin "rebellious" (see mutiny (n.)). As a verb from 1680s.
mutinous (adj.): 1570s, from mutine (see mutiny) + -ous. Related: Mutinously; mutinousness.
mutiny (n.): 1560s, with noun suffix -y (4) + obsolete verb mutine "revolt" (1540s), from Middle French mutiner "to revolt," from meutin "rebellious," from meute "a revolt, movement," from Vulgar Latin *movita "a military uprising," from fem. past participle of Latin movere "to move" (see move (v.)).
mutiny (v.): 1580s, from mutiny (n.). Alternative mutine is recorded from 1550s. Related: Mutinied; mutinying.
mutism (n.): "state of being mute," 1824, from French mutisme (1741), from Latin mutus (see mute (adj.)).
mutt (n.): 1901, "stupid or foolish person," probably a shortening of muttonhead (1803) in the same sense; see mutton and compare meathead, etc. Mutt was used by 1898 of a dog, especially a stupid one, and perhaps this is the same word formed independently (muttonhead also was used of stupid animals), or else a separate word of unknown derivation. Wright's "English Dialect Dictionary" (1900) has "Mutton! used in scolding a dog, prob. in allusion to the offence of sheep-worrying."
"That dog ain't no mutt," McManus would say as he stood behind the bar opening oysters; "no an he ain't no rube! Say! he's in it all the time when Charley trims the steaks." [Robert W. Chambers, "The Haunts of Men," 1898]
Used by 1910 in dog fancier publications to refer to a non-purebred animal.
Mutt and Jeff: comic strip characters Augustus Mutt and Jim Jeffries, in U.S. cartoonist Henry Conway ("Bud") Fisher's strip, which debuted in 1907. Used allusively from 1917 in reference to "a pair of stupid men, affable losers," or to one tall (Mutt) and one short (Jeff).
mutter (v.): early 14c., moteren "to mumble," from a common PIE imitative *mut- "to grunt, mutter" (source also of Old Norse muðla "to murmur," Latin muttire "to mutter," Old High German mutilon "to murmur, mutter; to drizzle"), with frequentative suffix -er. Related: Muttered; muttering.
mutter (n.): 1630s, from mutter (v.).
mutton (n.): "flesh of sheep used as food," late 13c., from Old French moton "mutton; ram, wether, sheep" (12c., Modern French mouton), from Medieval Latin multonem (8c.), probably from Gallo-Roman *multo-s, accusative of Celtic *multo "sheep" (source also of Old Irish molt "wether," Mid-Breton mout, Welsh mollt); the same word also was borrowed into Italian as montone "a sheep." Transferred slang sense of "food for lust, loose women, prostitutes" (1510s) led to extensive British slang uses down to the present day for woman variously regarded as seeking lovers or as lust objects. Mutton chop is from 1720; as a style of side whiskers, from 1865.
mutual (adj.): late 15c., originally of feelings, from Middle French mutuel (14c.), from Latin mutuus "reciprocal, done in exchange," from PIE root *mei- (1) "to change, exchange" (see mutable).
That is common which pertains equally to two or more persons or things.
That is mutual which is freely interchanged: mutual love, affection, hatred. The word is sometimes incorrectly used for common: our mutual friend, a phrase of very frequent occurrence, no doubt owing to the perfectly correct 'mutual friendship.'
[J.H.A. Günther, "English Synonyms Explained & Illustrated," Groningen, 1904]
Mutual Admiration Society (1851) seems to have been coined by Thoreau. Mutual fund is recorded from 1950. The Cold War's mutual assured destruction attested from 1966. (Assured destruction was an early 1960s term in U.S. military policy circles in reference to nuclear weapons as a deterrent, popularized c. 1964 by Robert McNamara, U.S. Secretary of Defense under Lyndon Johnson, e.g. statement before House Armed Services Committee, Feb. 18, 1965; the mutual perhaps first added by Donald Brennan, conservative defense analyst and a public critic of the policy, who also noted the acronym MAD.)
mutual (n.): short for mutual fund, 1971; see mutual.
mutualism (n.): 1849, in reference to the doctrine of French anarchist/socialist Pierre-Joseph Proudhon (1809-1865), from French mutuellisme. In biology, from 1876, from mutual + -ism.
mutualistic (adj.): 1885, from mutualist "advocate of mutualism" (1848); see mutualism.
mutuality (n.): 1580s, from mutual + -ity.
mutually (adv.): 1530s, from mutual + -ly (2). Mutually exclusive is recorded by 1650s.
muumuu (n.): also muu-muu, 1923, from Hawaiian mu'u mu'u, literally "cut off," name given to the local adaptation of the dresses given to Island women by early 19c. Christian missionaries "in the early days when a few flowers sufficed for a garment" [Don Blanding, "Hula Moons," 1930]. So called because the native style hangs from the shoulder and omits the high neck and the train.
Muzak (n.): 1935, proprietary name for piped music, supposedly a blend of music and Kodak, said to have been coined c. 1922 by Gen. George Squier, who developed the system of background music for workplaces.
muzzle (n.): late 14c., "device put over an animal's mouth to stop it from biting, eating, or rooting," from Old French musel "muzzle," also "snout, nose" (12c., Modern French museau), from muse "muzzle," from Gallo-Roman *musa "snout" (source also of Provençal mus, Old Spanish mus, Italian muso), of unknown origin, possibly related to Latin morsus "bite" (but OED finds "serious difficulties" with this). Meaning "projecting part of the head of an animal" is from early 15c. in English; sense of "open end of a firearm" first recorded 1560s.
muzzle (v.): "to put a muzzle on," early 15c., from muzzle (n.). Figurative use from 1610s. Related: Muzzled; muzzling.
muzzy (adj.): "confused, dazed," 1720s, perhaps from mossy, or from dialectal mosey (adj.) "moldy, hazy; stupefied with drink, dull, stupid."
mwah: sound indicative of a kiss or an air-kiss, 1994, imitative.
my (pron.): c. 1200, mi, reduced form of mine used before words beginning in consonants except h- (my father, but mine enemy), and from 14c. before all nouns. As interjection, by 1825, probably a shortened form of my God!
myalgia (n.): "muscular pain," 1827, coined in Modern Latin (on analogy of neuralgia) from myo- "muscle" + -algia "pain."
Myanmar: an old name for a part of Burma and a word for the country in native speech, officially chosen by military rulers of Burma in 1989. Reasons given include casting off a relic of colonialism, or downplaying of the connection to the Burman ethnic majority.
It should be pointed out that this renaming has virtually no impact on Burmese citizens speaking in Burmese, who continue to refer to both Myanma as well as Bama (this not unlike formal reference in the English language to 'The Netherlands' while informally using 'Holland'). [Gustaaf Houtman, "Mental Culture in Burmese Crisis Politics," 1999]
myasthenia (n.): "muscular weakness," 1856, medical Latin; see myo- + asthenia.
Mycenaean: 1590s, "pertaining to Mycenae," the ancient city on the Argive plain, from Latin Mycenaeus, from Greek Mykenaios "of Mycenae," from Mykenai. In reference to the Aegean civilization that flourished 1500-1100 B.C.E. and was centered on Mycenae, it is from 1890s.
myco-: before vowels myc-, word-forming element meaning "mushroom, fungus," formed irregularly from Greek mykes "fungus, mushroom, anything shaped like a mushroom," from PIE root *meug- "slimy, slippery" (see mucus). The correct form is myceto- (mycet-).
mycology (n.): 1822, from myco- + -logy. Related: Mycological; mycologist.
mycosis (n.): 1876, medical Latin; see myco- + -osis. Related: Mycotic.
myelin (n.): also myeline, "soft material found in nerve tissues," 1867, from German Myelin (1854), from Greek myelos "marrow; the brain, innermost part," of unknown origin.
myelo-: before vowels myel-, word-forming element meaning "marrow, spinal cord," from Greek myelos "marrow; the brain," of unknown origin.
myeloma (n.): 1857, from Greek myelos "marrow" + -oma.
Mylar (n.): proper name for a polyester film, 1954, trademarked by E.I. Du Pont de Nemours and Co., Wilmington, Delaware, U.S.A. Like many Du Pont names, it doesn't mean anything, they just liked the sound.
mynah (n.): type of passerine bird of India and the East, "talking starling," 1769, from Hindi maina "a starling," from Sanskrit madana- "delightful, joyful," related to madati "it gladdens," literally "it bubbles," from PIE root *mad- "moist, wet" (see mast (n.2).
myo-: before vowels my-, word-forming element meaning "muscle," from comb. form of Greek mys "muscle," literally "mouse" (see muscle (n.)).
myocardium (n.): 1866, from myo- + Latinized form of Greek kardia "heart," from PIE root *kerd- "heart" (see heart). Related: Myocardial; myocarditis.
myology (n.): 1640s; see myo- + -logy. Related: Myologist.
myomancy (n.): 1725, divination by the movements of mice, from Greek myo-, comb. form of mys (see mouse (n.)) + -mancy.
myope (n.): "short-sighted person," 1728, from French myope "short-sighted" (16c.), from Late Latin myop-, from Greek myops "short-sighted" (see myopia).
myopia (n.): "short-sightedness," 1727, medical Latin, from Late Greek myopia "near-sightedness," from myops "near-sighted," literally "closing the eyes," from myein "to shut" (see mute (adj.)) + ops (genitive opos) "eye" (see eye (n.)).
myopic (adj.): "short-sighted," 1800, from myopia + -ic. Figurative use from 1891. Related: Myopical (1748); myopically.
myriad (n.): 1550s, from Middle French myriade and directly from Late Latin myrias (genitive myriadis) "ten thousand," from Greek myrias (genitive myriados) "a number of ten thousand, countless numbers," from myrios (plural myrioi) "innumerable, countless, infinite; boundless," as a definite number, "ten thousand" ("the greatest number in Greek expressed by one word," Liddell & Scott say), of unknown origin; perhaps from PIE *meue- "abundant" (source also of Hittite muri- "cluster of grapes," Latin muto "penis," Middle Irish moth "penis"). Specific use is usually in translations from Greek or Latin.
myriad (adj.): c. 1800, from myriad (n.).
myrmidon (n.): c. 1400, from Latin Myrmidones (plural), from Greek Myrmidones, Thessalian tribe led by Achilles to the Trojan War, fabled to have been ants changed into men, and often derived from Greek myrmex "ant" (from PIE *morwi- (see Formica (2)), but Watkins does not connect them and Klein's sources suggest a connection to Greek mormos "dread, terror." Transferred sense of "faithful follower" is from c. 1600.