Online Etymology Dictionary

muggy (adj.): 1731, from mugen "to drizzle" (late 14c.), from a Scandinavian source such as Old Norse mugga "drizzling mist," possibly from PIE *meug- "slimy, slippery" (see mucus).
Mughal: variant transliteration of mogul (n.1).
mugshot (n.): also mug shot, 1950; see mug (n.2) + shot (n.) in the photographic sense.
mugwort (n.): Old English mugcwyrt, literally "midge wort," from Proto-Germanic *muggiwurti, from *muggjo- "fly" (see midge) + root of wort.
mugwump (n.): 1832, jocular for "great man, boss, important person," American English, from Algonquian (Natick) mugquomp "important person" (derived from mugumquomp "war leader"); used from 1884 of Republicans who refused to support James G. Blaine's presidential candidacy, hence "one who holds himself aloof from party politics."
Muhammad: 1610s, Mohammed, Arabic masc. proper name, literally "the Praiseworthy," name of the prophet of Islam (c.570-632). The earliest forms of his name in English were Mahum, Mahimet (c. 1200); originally also used confusedly for "an idol." Wyclif has Macamethe (c. 1380), and Makomete also turns up in 14c. documents. Mahomet was common until 19c.; see Mohammed.
mujahidin (n.): also mujahideen, 1958, in a Pakistani context, from Persian and Arabic, plural of mujahid "one who fights in a jihad" (q.v.); in modern use, "Muslim guerilla insurgent."
mulatto (n.): 1590s, "offspring of a European and a black African," from Spanish or Portuguese mulato "of mixed breed," literally "young mule," from mulo "mule," from Latin mulus (fem. mula) "mule" (see mule (n.1)); possibly in reference to hybrid origin of mules (compare Greek hemi-onos "a mule," literally "a half-ass;" as an adjective, "one of mixed race"). As an adjective from 1670s. Fem. mulatta is attested from 1620s; mulattress from 1805.
American culture, even in its most rigidly segregated precincts, is patently and irrevocably composite. It is, regardless of all the hysterical protestations of those who would have it otherwise, incontestibly mulatto. Indeed, for all their traditional antagonisms and obvious differences, the so-called black and so-called white people of the United States resemble nobody else in the world so much as they resemble each other. [Albert Murray, "The Omni-Americans: Black Experience & American Culture," 1970]
Old English had sunderboren "born of disparate parents."
mulberry (n.): late 14c., developed from 13c. morberie, or cognate Middle High German mul-beri (alteration by dissimilation of Old High German mur-beri, Modern German Maulbeere); both from Latin morum "mulberry, blackberry," + Old English berie, Old High German beri "berry." The Latin word probably is from Greek moron "mulberry," from PIE *moro- "blackberry, mulberry" (source also of Armenian mor "blackberry," Middle Irish merenn, Welsh merwydden "mulberry"). Children's singing game with a chorus beginning "Here we go round the mulberry bush" is attested from 1820s, first in Scotland.
mulch (n.): 1650s, probably from a noun use of Middle English molsh (adj.) "soft, moist" (early 15c.), from Old English melsc, milisc "mellow, sweet," from Proto-Germanic *mil-sk- (source also of Dutch mals "soft, ripe," Old High German molawen "to become soft," German mollig "soft"), from PIE root *mel- "soft" (see mild).
mulch (v.): 1802, from mulch (n.). Related: Mulched; mulching.
mulct (v.): late 15c., "to punish by a fine," from Middle French mulcter "to fine, punish" (15c.), from Latin mulctare, altered (Barnhart calls it "false archaism") from multare "punish, to fine," from multa "penalty, fine," perhaps from Oscan or Samnite [Klein]. Sense of "defraud" is first recorded 1748. Related: Mulcted; mulcting.
mule (n.1): "offspring of donkey and horse," from Old English mul, Old French mul "mule, hinny" (12c., fem. mule), both from Latin mulus (fem. mula) "a mule," probably from a pre-Latin Mediterranean language.
The mule combines the strength of the horse with the endurance and surefootedness of the ass, and is extensively bred for certain employments for which it is more suited than either; it is ordinarily incapable of procreation. With no good grounds, the mule is a proverbial type of obstinacy. [OED]
Properly, the offspring of a he-ass and a mare; that of a she-ass and a stallion is technically a hinny. Used allusively of hybrids and things of mixed nature. As a type of spinning machine, attested from 1797 (so called because a hybrid of distinct warp and woof machines). Meaning "obstinate, stupid, or stubborn person" is from 1470s; that of "narcotics smuggler or courier" first attested 1935.
mule (n.2): "loose slipper," 1560s, from Middle French mule, from Latin mulleus calceus "red high-soled shoe," worn by Roman patricians, from mullus "red" (see mullet (n.1)). Related: Mules.
muleteer (n.): "mule driver," 1530s, from Middle French muletier, from mulet "mule," a diminutive formation replacing Old French mul as the word for "mule" in French (see mule (n.1)).
mulish (adj.): 1751, from mule (n.1) + -ish. Related: Mulishly; mulishness.
mull (v.1): "ponder," 1873, perhaps from a figurative use of Middle English mullyn "grind to powder, pulverize," from molle "dust, ashes, rubbish" (c. 1300), probably from Middle Dutch mul "grit, loose earth," related to mill (n.1). But Webster's (1879) defined it as "to work steadily without accomplishing much," which may connect it to earlier identical word in athletics sense of "to botch, muff" (1862). Related: Mulled; mulling.
mull (v.2): "sweeten, spice and heat a drink," c. 1600, of unknown origin, perhaps from Dutch mol, a kind of white, sweet beer, or from Flemish molle a kind of beer, and related to words for "to soften." Related: Mulled; mulling.
mull (n.): "promontory" (in Scottish place names), late 14c., perhaps from Old Norse muli "a jutting crag, projecting ridge (between two valleys)," which probably is identical with muli "snout, muzzle." The Norse word is related to Old Frisian mula, Middle Dutch mule, muul, Old High German mula, German Maul "muzzle, mouth." Alternative etymology traces it to Gaelic maol "brow of a hill or rock," also "bald," from Old Celtic *mailo-s (source also of Irish maol, Old Irish máel, máil, Welsh moel).
mullah (n.): title given in Muslim lands to one learned in theology and sacred law, 1610s, from Turkish molla, Persian and Urdu mulla, from Arabic mawla "master," from waliya "reigned, governed."
mullein (n.): tall plant of the figwort family, mid-15c., from Anglo-French moleine (French moulaine), perhaps literally "the soft-leaved plant," from French mol "soft," from Latin mollis (see melt (v.))
mullet (n.1): edible type of spiny-finned fish, mid-15c., from Anglo-French molett (late 14c.), Old French mulet, from Medieval Latin muletus, from Latin mulettus, from mullus "red mullet," from Greek myllos a marine fish, related to melos "black," from PIE *mel- "of darkish color" (see melanin).
mullet (n.2): "hairstyle short on top and long in back," 1996, perhaps from mullet-head "stupid, dull person" (1857). Also the name of a type of North American freshwater fish with a large, flat head (1866). The term in reference to the haircut seems to have emerged into pop culture with the Beastie Boys song "Mullet Head."
#1 on the side and don't touch the back
#6 on the top and don't cut it wack, Jack
[Beastie Boys, "Mullet Head"]
As a surname, Mullet is attested from late 13c., thought to be a diminutive of Old French mul "mule." Compare also mallet-headed, in reference to the flat tops of chisels meant to be struck with a mallet.
Mulligan (n.): surname, from Gaelic Maolagan, Old Irish Maelecan, a double diminutive of mael "bald," hence "the little bald (or shaven) one," probably often a reference to a monk or disciple. As "stew made with whatever's available," 1904, hobo slang, probably from a proper name. The golf sense of "extra stroke after a poor shot" (1949) is sometimes said to be from the name of a Canadian golfer in the 1920s whose friends gave him an extra shot in gratitude for driving them over rough roads to their weekly foursome at St. Lambert Country Club near Montreal.
mulligrubs (n.): "fit of the blues," also "colic," 1590s, mulliegrums, fanciful formation.
mullion (n.): "vertical column between the lights of a window," 1560s, metathesis of Middle English moyniel (early 14c.), from Anglo-French moinel, noun use of moienel (adj.) "middle," from Old French meien "intermediate, mean" (see mean (adj.)). Related: Mullioned.
multi-: before vowels mult-, word-forming element meaning "many, many times, much," from comb. form of Latin multus "much, many," from PIE *ml-to-, from root *mel- "strong, great, numerous" (source also of Latin melior "better," Greek mala "very, very much"). Many words that use it (multinational, etc.) are 20c. coinages.
multi-millionaire (n.): also multimillionaire, 1858, from multi- + millionaire.
multi-ply (adj.): 1950, from multi- + ply (n.).
multi-use (adj.): 1952, from multi- + use (n.).
multicellular (adj.): also multi-cellular, 1857, from multi- + cellular.
multicolored (adj.): also multi-colored, multi-coloured, 1845, from multi- + colored.
multicultural (adj.): also multi-cultural, 1941, from multi- + cultural. At first often in a Canadian context. Picked up by U.S. education writers 1980s; widespread popular use from c. 1990.
multiculturalism (n.): 1965, from multicultural + -ism.
multidimensional (adj.): also multi-dimensional, 1884, from multi- + dimensional (see dimension).
multidisciplinary (adj.): also multi-disciplinary, 1949, from multi- + disciplinary.
multifaceted (adj.): also multi-faceted, 1870, from multi- + faceted (see facet).
multifactorial (adj.): also multi-factorial, 1920, from multi- + factorial.
multifarious (adj.): 1590s, from Latin multifarius "manifold," from multifariam (adv.) "on many sides; in many places or parts," perhaps originally "that which can be expressed in many ways," from multi- "many" (see multi-) + -fariam, adverbial suffix (compare bifariam "in two places"), from PIE *dwi-dhe- "making two." Related: Multifariously; multifariousness. Earlier forms of the word in English were multiphary (adv.); multipharie (adj.), both mid-15c.
multiflora (n.): 1829, from Latin multiflora (rosa), from fem. of multiflorus, from multi- (see multi-) + flor-, stem of flos (see florid).
multifloral (adj.): 1875, from Late Latin multiflorus (see multiflora) + -al (1).
multiform (adj.): also multi-form, c. 1600, from French multiforme or Latin multiformis "many-shaped, manifold," from multus "much, many" (see multi-) + forma "shape" (see form (n.)).
multiformity (n.): 1580s, from Late Latin multiformitas, from multiformis; see multi- + form (n.).
multilateral (adj.): also multi-lateral, 1690s, in geometry, "having many sides," from multi- + Latin latus (genitive lateris) "side" (see oblate (n.)). Figurative use by 1748. Meaning "pertaining to three or more countries" is from 1802. Related: Multilaterally.
multilateralism (n.): 1928, from multilateral + -ism.
multilayer (adj.): also multi-layer, 1923, from multi- + layer (n.).
multilevel (adj.): also multi-level, 1952, from multi- + level.
multilineal (adj.): also multi-lineal, 1800, from multi- + lineal.
multilingual (adj.): also multi-lingual, 1838, from multi- + Latin lingua "language," literally "tongue" (see lingual). Related: Multilingually; multilingualism.
multimedia (adj.): also multi-media, 1962, from multi- + media.