Online Etymology Dictionary

municipality (n.): 1789, from French municipalité, from municipal (see municipal).
munificence (n.): early 15c., from Middle French munificence, from Latin munificentia "bountifulness, liberality, generosity," from stem of munificus "generous, bountiful, liberal," literally "present-making," from munus "gift or service, duty, office" (see municipal) + unstressed stem of facere "to do" (see factitious).
munificent (adj.): 1580s, back-formation from munificence, or else from Latin munificent-, stem of munificus "bountiful, liberal, generous" (see munificence).
munition (n.): mid-15c., from Middle French municion "fortification, defense, defensive wall" (14c.), from Latin munitionem (nominative munitio) "a defending, fortification, protecting," noun of action from past participle stem of munire "to fortify," from moenia "defensive walls," related to murus "wall" (see mural). By 1530s the sense had passed through "military stores" to become "ammunition."
Munsell: system of color classification, 1905, named for U.S. painter and professor Albert H. Munsell (1858-1918), who developed it.
Munster: type of cheese; see Muenster.
Muppet (n.): Trademark (U.S.) Sept. 26, 1972, claiming use from 1971, but in print from Sept. 1970. Name coined by creator Jim Henson (1936-1990), who said, despite the resemblance to marionette and puppet (they have qualities of both), it has no etymology; he just liked the sound.
mural (n.): painting on a wall, 1921, short for mural painting (1850), from mural (adj.) "pertaining to walls" (mid-15c.), from Latin muralis "of a wall," from murus "wall" (Old Latin moiros, moerus), from PIE *mei- "to fix; to build fences or fortifications" (source also of Old English mære "boundary, border, landmark;" Old Norse -mæri "boundary, border-land;" Latin munire "to fortify, protect").
murder (n.): c. 1300, murdre, from Old English morðor (plural morþras) "secret killing of a person, unlawful killing," also "mortal sin, crime; punishment, torment, misery," from Proto-Germanic *murthra- (source also of Goth maurþr, and, from a variant form of the same root, Old Saxon morth, Old Frisian morth, Old Norse morð, Middle Dutch moort, Dutch moord, German Mord "murder"), from PIE *mrtro-, from root *mer- "to die" (see mortal (adj.)). The spelling with -d- probably reflects influence of Anglo-French murdre, from Old French mordre, from Medieval Latin murdrum, from the Germanic root.

Viking custom, typical of Germanic, distinguished morð (Old Norse) "secret slaughter," from vig (Old Norse) "slaying." The former involved concealment, or slaying a man by night or when asleep, and was a heinous crime. The latter was not a disgrace, if the killer acknowledged his deed, but he was subject to vengeance or demand for compensation.
Mordre wol out that se we day by day. [Chaucer, "Nun's Priest's Tale," c. 1386]
Weakened sense of "very unpleasant situation" is from 1878.
murder (v.): Old English myrðrian, from Proto-Germanic *murthjan (source also of Old High German murdran, German mördren, Gothic maurþjan; see murder (n.)). Related: Murdered; murdering.
murderer (n.): mid-14c., alteration of murtherer (c. 1300), agent noun from murder (v.); in part from Old French mordrere, from Medieval Latin murdrarius, from Germanic. Old English words for this included morðorcwalu, morðorslaga, morðorwyrhta, literally "murder-wright." The original murderer's row was in New York City's Tombs prison; figurative use in baseball dates to 1858, though the quintessential one was the 1927 New York Yankees. Fem. form murderess attested from late 14c. Murderee (1920) never caught on.
murderous (adj.): 1530s, a hybrid from murder + -ous. An Old English word for it was morðorhycgende. Related: Murderously; murderousness.
murex (n.): kind of shellfish which yields a purple dye, 1580s, from Latin murex (plural murices) "purple fish, purple dye," probably cognate with Greek myax "sea mussel," of unknown origin, perhaps related to mys "mouse" (see muscle (n.) and mussel).
Muriel: fem. proper name, probably Celtic and meaning literally "sea bright;" compare Welsh Meriel, Meryl, Irish Muirgheal, earlier Muirgel, from muir "sea" (see mere (n.)) + geal "bright."
murine (adj.): c. 1600, from Latin murinus, from mus "mouse" (see mouse (n.)).
murk (n): c. 1300, myrke, from Old Norse myrkr "darkness," from Proto-Germanic *merkwjo- (source also of Old English mirce "murky, black, dark; murkiness, darkness," Danish mǿrk "darkness," Old Saxon mirki "dark"); cognate with Old Church Slavonic mraku, Serbo-Croatian mrak, Russian mrak "darkness;" Lithuanian merkti "shut the eyes, blink," from PIE *mer- "to flicker" (see morn). Murk Monday was long the name in Scotland for the great solar eclipse of March 29, 1652 (April 8, New Style).
murky (adj.): mid-14c., from murk + -y (2). Rare before 17c. Related: Murkily; murkiness.
murmur (n.): late 14c., "expression of discontent by grumbling," from Old French murmure "murmur, sound of human voices; trouble, argument" (12c.), noun of action from murmurer "to murmur," from Latin murmurare "to murmur, mutter," from murmur (n.) "a hum, muttering, rushing," probably from a PIE reduplicative base *mor-mor, of imitative origin (source also of Sanskrit murmurah "crackling fire," Greek mormyrein "to roar, boil," Lithuanian murmlenti "to murmur"). Meaning "softly spoken words" is from 1670s.
murmur (v.): late 14c., from Old French murmurer "murmur, grouse, grumble" (12c.), from murmur "rumbling noise" (see murmur (n.)). Related: Murmured; murmuring.
murmuring (n.): late 14c., verbal noun from murmur (v.).
Murphy: Gaelic Murchadh "sea-warrior." The Celtic "sea" element is also in names Muriel (q.v.), Murdoch (Old Irish Muireadhach, Old Welsh Mordoc "mariner"), etc. Murphy bed (1925) is named for U.S. inventor William Lawrence Murphy (1876-1959). By happy coincidence, Murphy was an illiterate 18c.-19c. perversion of Morpheus, god of sleep.
Murphy's law: 1958, used of various pessimistic aphorisms. If there ever was a real Murphy his identity is lost to history. Said to be military originally, and probably pre-dates the earliest printed example (the 1958 citation calls it "an old military maxim").
murrain (n.): "cattle plague," early 14c., from Anglo-French moryn, Old French moraine "pestilence" (12c.), probably from mourir "to die," from Latin mori (see mortal (adj.)).
muscat (n.): type of wine, 1570s, from French, from Italian moscato, literally "musky-flavored," from Vulgar Latin *muscatus, from Latin muscus (see musk).
Muscat: capital of Oman, from Arabic Masqat, said to mean "hidden" (it is isolated from the interior by hills).
muscatel (n.): 1530s, variant of muskadell (c. 1400), from Old French muscadel, from Old Provençal *muscadel, diminutive of muscat "(grape) with the fragrance of musk" (see muscat).
muscle (n.): late 14c., from Middle French muscle "muscle, sinew" (14c.) and directly from Latin musculus "a muscle," literally "little mouse," diminutive of mus "mouse" (see mouse (n.)).

So called because the shape and movement of some muscles (notably biceps) were thought to resemble mice. The analogy was made in Greek, too, where mys is both "mouse" and "muscle," and its comb. form gives the medical prefix myo-. Compare also Old Church Slavonic mysi "mouse," mysica "arm;" German Maus "mouse; muscle," Arabic 'adalah "muscle," 'adal "field mouse." In Middle English, lacerte, from the Latin word for "lizard," also was used as a word for a muscle.
Musclez & lacertez bene one selfe þing, Bot þe muscle is said to þe fourme of mouse & lacert to þe fourme of a lizard. [Guy de Chauliac, "Grande Chirurgie," c. 1425]
Hence muscular and mousy are relatives, and a Middle English word for "muscular" was lacertous, "lizardy." Figurative sense of "force, violence, threat of violence" is 1930, American English. Muscle car "hot rod" is from 1969.
muscle (v.): 1913, "to accomplish by strength," from muscle (n.). Related: Muscled; muscling. To muscle in is 1929 in underworld slang.
muscle-bound (adj.): 1879, from muscle (n.) + bound, past participle of bind (v.).
muscle-man (n.): 1929, originally "an underworld enforcer;" sense of "strong man" first attested 1952; from muscle (n.) + man (n.).
muscled (adj.): "having muscles (of a particular type)," 1640s, from muscle (n.).
Muscovy: from French Moscovie, from Modern Latin Moscovia, old name of Russia, from Russian Moskova "(Principality of) Moscow." In Muscovy duck (1650s) and certain other uses it is a corruption of musk. Related: Muscovite.
muscular (adj.): 1680s, "pertaining to muscles," from Latin musculus (see muscle (n.)) + -ar. Earlier in same sense was musculous (early 15c.). Meaning "having well-developed muscles" is from 1736. Muscular Christianity (1857) is originally in reference to philosophy of Anglican clergyman and novelist Charles Kingsley (1819-1875). Muscular dystrophy attested from 1886.
muscularity (n.): 1680s, from Modern Latin muscularis (from Latin musculus; see muscle (n.)) + -ity.
musculature (n.): "system of muscles," 1875, from French musculature, from Latin musculus (see muscle (n.)).
musculo-: word-forming element meaning "involving or pertaining to muscles," from comb. form of Latin musculus "muscle" (see muscle (n.)).
musculoskeletal (adj.): 1944, from musculo- + skeletal.
muse (v.): "to reflect, to be absorbed in thought," mid-14c., from Old French muser (12c.) "to ponder, dream, wonder; loiter, waste time," literally "to stand with one's nose in the air" (or, possibly, "to sniff about" like a dog who has lost the scent), from muse "muzzle," from Gallo-Roman *musa "snout," of unknown origin. Probably influenced in sense by muse (n.). Related: Mused; musing.
muse (n.): late 14c., protectors of the arts, from Old French Muse and directly from Latin Musa, from Greek Mousa, "the Muse," also "music, song," from PIE root *men- "to think, remember" (see mind (n.)). Meaning "inspiring goddess of a particular poet" is from late 14c. The traditional names and specialties of the nine Muses, daughters of Zeus and Mnemosyne, are: Calliope (epic poetry), Clio (history), Erato (love poetry, lyric art), Euterpe (music, especially flute), Melpomene (tragedy), Polymnia (hymns), Terpsichore (dance), Thalia (comedy), Urania (astronomy).
musette (n.): "small bagpipe," late 14c., from Old French musette "bagpipe" (13c.), from muser "to play the bagpipe, make music," from mus "mouth, muzzle," from Medieval Latin musum (see muzzle (n.)). As "a composition for a musette" from 1811, from French.
museum (n.): 1610s, "the university building in Alexandria," from Latin museum "library, study," from Greek mouseion "place of study, library or museum, school of art or poetry," originally "a seat or shrine of the Muses," from Mousa "Muse" (see muse (n.)). Earliest use in reference to English institutions was of libraries (such as the British Museum); sense of "building to display objects" first recorded 1680s.
mush (n.): "kind of porridge," 1670s, in the American colonies, variant of mash (n.) "soft mixture." Meaning "anything soft and thick" is attested from 1824.
mush (interj.): command to sled dogs, first recorded 1862, as mouche, perhaps altered from French marchons! "advance!" (imperative of marcher "to march;" see march (v.)).
mush (v.): "to pound to a pulp," 1781, from mush (n.). Related: Mushed; mushing.
mushiness (n.): 1890, from mushy + -ness. Figurative sense of "sentimentality" attested from 1946.
mushroom (n.): mid-15c., muscheron, musseroun (attested 1327 as a surname, John Mussheron), from Anglo-French musherun, Old French meisseron (11c., Modern French mousseron), perhaps from Late Latin mussirionem (nominative mussirio), though this might as well be borrowed from French. Barnhart says "of uncertain origin." Klein calls it "a word of pre-Latin origin, used in the North of France;" OED says it usually is held to be a derivative of French mousse "moss" (from Germanic), and Weekley agrees, saying it is properly "applied to variety which grows in moss," but Klein says they have "nothing in common." For the final -m Weekley refers to grogram, vellum, venom. Modern spelling is from 1560s.

Used figuratively for something or someone that makes a sudden appearance in full form from 1590s. In reference to the shape of clouds after explosions, etc., it is attested from 1916, though the actual phrase mushroom cloud does not appear until 1955.
mushroom (v.): "expand or increase rapidly," 1741, from mushroom (n.). Related: Mushroomed; mushrooming.
mushy (adj.): "soft, pulpy, 1839; "sentimental," 1870; from mush (n.) + -y (2). Mush (n.) in a transferred sense of "sentimentality" is attested from 1908.
music (n.): mid-13c., musike, from Old French musique (12c.) and directly from Latin musica "the art of music," also including poetry (also source of Spanish musica, Italian musica, Old High German mosica, German Musik, Dutch muziek, Danish musik), from Greek mousike (techne) "(art) of the Muses," from fem. of mousikos "pertaining to the Muses," from Mousa "Muse" (see muse (n.)). Modern spelling from 1630s. In classical Greece, any art in which the Muses presided, but especially music and lyric poetry.

The use of letters to denote music pitch probably is at least as old as ancient Greece, as their numbering system was ill-suited to the job. Natural scales begin at C (not A) because in ancient times the minor mode was more often used than the major one, and the natural minor scale begins at A.

Music box is from 1773, originally "barrel organ;" music hall is from 1842, especially "hall licensed for musical entertainment" (1857). To face the music "accept the consequences" is from 1850; the exact image is uncertain, one theory ties it to stage performers, another to cavalry horses having to be taught to stay calm while the regimental band plays. To make (beautiful) music with someone "have sexual intercourse" is from 1967.
musical (adj.): early 15c., "pertaining to music; tuneful, harmonious; adept at making music," from Middle French musical (14c.) and directly from Medieval Latin musicalis, from Latin musica (see music). Musical box is from 1829. Children's game musical chairs is attested from 1877, hence use of musical as a modifier meaning "changing rapidly from one to another possessor" (1924). Related: Musically.