Online Etymology Dictionary

musical (n.): "theatrical piece in which music figures prominently," 1937, from musical (adj.) in musical play. Earlier as a noun it meant "musical instrument" (c. 1500), "musical performance" (1570s); "musical party" (1823, a sense now in musicale).
musicale (n.): "musical party," 1872, from French musicale, short for soirée musicale "musical evening (party);" see musical (adj.).
musicality (n.): 1812, from musical (adj.) + -ity.
musician (n.): late 14c., "one skilled in music," from Old French musicien (14c.), or a native formation from music + -ian. Sense of "professional musical performer" first recorded mid-15c.
musicianship (n.): 1828, from musician + -ship.
musico-: word-forming element from comb. form of Latin musicus (see music).
musicology (n.): "the study of the science of music," 1909, from music + -ology. Related: Musicological; musicologist.
musing (n.): late 14c., "complaint," verbal noun from muse (v.). Meaning "pondering" is from mid-15c. Related: Musingly; musings.
musk (n.): late 14c., from Old French musc (13c.) and directly from Late Latin muscus, from Late Greek moskhos, from Persian mushk, from Sanskrit muska-s "testicle," from mus "mouse" (so called, presumably, for resemblance; see muscle). The deer gland was thought to resemble a scrotum. German has moschos, from a Medieval Latin form of the Late Greek word. Spanish has almizcle, from Arabic al misk "the musk," from Persian. Applied to various plants and animals of similar smell (such as musk-ox, 1744).
muskeg (n.): kind of moss bog, 1865, from a Cree Indian word.
muskellunge (n.): "large North American pike," 1789, from Algonquian (Ojibwa) maashkinoozhe; the second element kinoozhe "pike;" the first either mac "great," maazh- "similar to," or maazh- "ugly." Altered by French folk etymology as masque allongé "long mask." Called muskie for short (1894).
musket (n.): "firearm for infantry" (later replaced by the rifle), 1580s, from Middle French mousquette, also the name of a kind of sparrow-hawk, diminutive of mosca "a fly," from Latin musca (see midge). The hawk so called either for its size or because it looks speckled when in flight. Early firearms often were given names of beasts (compare dragoon, also falcon, a kind of cannon mentioned by Hakluyt), and the equivalent word in Italian was used to mean "an arrow for a crossbow." The French word was borrowed earlier into English (early 15c.) in its literal sense of "sparrow-hawk."
musketeer (n.): "soldier armed with a musket," 1580s, from musket + -eer, or else from French mousquetaire, from mousquette (see musket).
musketry (n.): 1640s, from French mousqueterie, from mousquet "musket" (see musket), on analogy of Italian moschetteria.
Muskoegan: North American Indian language family, 1891, from Creek maskoki.
muskrat (n.): also musk-rat, 1610s, alteration (by association with musk and rat) of musquash, from Algonquian (probably Powhatan) muscascus, literally "it is red," so called for its colorings. From cognate Abenaki muskwessu comes variant form musquash (1620s).
musky (adj.): c. 1600, from musk + -y (2). Related: Muskiness.
musky (n.): late 19c., short for muskrat or muskellunge. Also muskie.
Muslim (n.): 1610s, from Arabic muslim "one who submits" (to the faith), from root of aslama "he resigned." Related to Islam. From 1777 as an adjective.
muslin (n.): c. 1600, "delicately woven cotton fabric," from French mousseline (17c.), from Italian mussolina, from Mussolo, Italian name of Mosul, city in northern Mesopotamia (modern Iraq) where muslin was made. Like many fabric names, it has changed meaning over the years, in this case from luxurious to commonplace. In 13c. French, mosulin meant "cloth of silk and gold." The meaning "everyday cotton fabric for shirts, bedding, etc." is first attested 1872 in American English.
muss (v.): "to make untidy," 1837, probably a variant of mess in its sense of "disorder." Earlier (1830) as a noun meaning "disturbance." Related: Mussed; mussing.
mussel (n.): Old English muscle, musscel "shellfish, mussel," from Late Latin muscula (source of Old French musle, Modern French moule, Middle Dutch mosscele, Dutch mossel, Old High German muscula, German Muschel), from Latin musculus "mussel," literally "little mouse," also "muscle;" like muscle, derived from mus "mouse" on the perceived similarity of size and shape. The modern spelling, distinguishing the word from muscle, first recorded c. 1600, not fully established until 1870s.
Mussulman (n.): "a Muslim," 1560s, from Turkish musulman, from Persian musulman (adj.), from Arabic muslim (see Muslim) + adjective suffix -an.
mussy (adj.): "rumpled," 1859, from muss + -y (2). Related: Mussiness.
must (v.): Old English moste, past tense of motan "have to, be able to," from Proto-Germanic *mot- "ability, leisure (to do something)" (source also of Old Saxon motan "to be obliged to, have to," Old Frisian mota, Middle Low German moten, Dutch moeten, German müssen "to be obliged to," Gothic gamotan "to have room to, to be able to"), perhaps from PIE root *med- "to measure, to take appropriate measures" (see medical (adj.)). Used as present tense from c. 1300, from the custom of using past subjunctive as a moderate or polite form of the present.
must (n.1): "new wine," Old English must, from Latin mustum (also source of Old High German, German most, Old French moust, Modern French moût, Spanish, Italian mosto), short for vinum mustum "fresh wine," neuter of mustus "fresh, new, newborn," perhaps literally "wet," and from PIE *mus-to-, from root *meus- "damp" (see moss).
must (n.2): "mold," c. 1600, perhaps a back-formation of musty (q.v.).
must (n.3): "male elephant frenzy," 1871, from Urdu mast "intoxicated, in rut," from Persian mast, literally "intoxicated," related to Sanskrit matta- "drunk, intoxicated," past participle of madati "boils, bubbles, gets drunk," from PIE root *mad- "wet, moist" (see mast (n.2)).
must (n.4): "that which has to be done, seen, or experienced," 1892, from must (v.). As an adjective, "obligatory, indispensable," by 1912, from the noun; must-read is from 1959.
mustache (n.): 1580s, from French moustache (15c.), from Italian mostaccio, from Medieval Greek moustakion, diminutive of Doric mystax (genitive mystakos) "upper lip, mustache," related to mastax "jaws, mouth," literally "that with which one chews," from PIE root *mendh- "to chew" (see mandible).

Borrowed earlier (1550s) as mostacchi, from the Italian word or its Spanish derivative mostacho. The plural form of this, mustachios, lingers in English. Slang shortening stache attested from 1985. Dutch slang has a useful noun, de befborstel, to refer to the mustache specifically as a tool for stimulating the clitoris; probably from beffen "to stimulate the clitoris with the tongue."
mustachioed (adj.): 1817, from mustachio (1550s), from Spanish mostacho and directly from Italian mostaccio (see mustache). The noun was superseded by mustache, but the adjective has endured.
mustang (n.): "small, half-wild horse of the American prairie," 1808, from Mexican Spanish mestengo "animal that strays" (16c.), from Spanish mestengo "wild, stray, ownerless," literally "belonging to the mesta," an association of cattle ranchers who divided stray or unclaimed animals that got "mixed" with the herds, from Latin mixta "mixed," fem. past participle of miscere "to mix" (see mix (v.)).

Said to be influenced by the Spanish word mostrenco "straying, wild," which is probably from mostrar, from Latin monstrare "to show."
mustard (n.): late 13c. (late 12c. as a surname), from Old French mostarde "mustard, mustard plant" (Modern French moutarde), from moust "must," from Latin mustum "new wine" (see must (n.1)); so called because it was originally prepared by adding must to the ground seeds of the plant to make a paste. As a color name, it is attested from 1848.

Mustard gas, World War I poison (first used by the Germans at Ypres, 1917), so called for its color and smell and burning effect on eyes and lungs; chemical name is dichlordiethyl sulfide, it contains no mustard, and is an atomized liquid, not a gas. To cut the mustard (1907, usually in negative) is probably from slang mustard "genuine article, best thing" (1903) on notion of "that which enhances flavor."
I'm not headlined in the bills, but I'm the mustard in the salad dressing just the same. [O.Henry, "Cabbages and Kings," 1904]
mustee (n.): "octoroon, offspring of a white and a quadroon," also "half-caste," 1690s, a corruption of Spanish mestizo (q.v.).
mustelid (n.): 1910, from Modern Latin Mustelidae, taken as a genus name by Linnaeus (1758), from Latin mustela "weasel," possibly related to mus "mouse" (see mouse (n.)). Tucker tentatively suggests *mus-ters-la "mouse harrier" and Klein notes that the weasel was identified in antiquity as "the catcher of mice."
musteline (adj.): "weasel-like; pertaining to weasels," 1650s, from Latin mustela (see mustelid) + -ine (1).
muster (v.): c. 1300, "to display, reveal, appear," from Old French mostrer "appear, show, reveal," also in a military sense (10c., Modern French montrer), from Latin monstrare "to show," from monstrum "omen, sign" (see monster). Meaning "to collect, assemble" is early 15c.; figurative use (of qualities, etc.) is from 1580s. To muster out "gather to be discharged from military service" is 1834, American English. To muster up in the figurative and transferred sense of "gather, summon, marshal" is from 1620s. Related: Mustered; mustering.
muster (n.): late 14c., "action of showing, manifestation," from Old French mostre "illustration, proof; examination, inspection" (13c., Modern French montre), literally "that which is shown," from mostrer (see muster (v.)). Meaning "act of gathering troops" is from c. 1400. To pass musters (1570s) originally meant "to undergo military review without censure."
mustn't: by mid-18c., contraction of must not; see must (v).
musty (adj.): 1520s, perhaps a variant of moisty "moist, damp" (see moist). Related: Mustiness.
mutability (n.): late 14c., "tendency to change, inconstancy," from Middle French mutabilité, from Latin mutabilitas, from mutabilis (see mutable).
mutable (adj.): late 14c., "liable to change," from Latin mutabilis "changeable," from mutare "to change," from PIE root *mei- (1) "to change, go, move" (source also of Sanskrit methati "changes, alternates, joins, meets;" Avestan mitho "perverted, false;" Hittite mutai- "be changed into;" Latin meare "to go, pass," migrare "to move from one place to another;" Old Church Slavonic mite "alternately;" Czech mijim "to go by, pass by," Polish mijać "avoid;" Gothic maidjan "to change"); with derivatives referring to the exchange of goods and services as regulated by custom or law (compare Latin mutuus "done in exchange," munus "service performed for the community, duty, work").
mutagen (n.): 1946, from mutation + -gen "thing that produces." Related: Mutagenic; mutagenesis; mutagenize.
mutant (n.): 1901, in the biological sense, from Latin mutantem (nominative mutans) "changing," present participle of mutare "to change" (see mutable). In the science fiction sense, it is attested from 1954. As an adjective from 1903.
mutate (v.): "to change state or condition," 1818, back-formation from mutation. In genetic sense, 1913, from Latin mutatus, past participle of mutare "to change" (see mutable). Related: Mutated; mutating.
mutation (n.): late 14c., "action of changing," from Old French mutacion (13c.), and directly from Latin mutationem (nominative mutatio) "a changing, alteration, a turn for the worse," noun of action from past participle stem of mutare "to change" (see mutable). Genetic sense is from 1894. The linguist's i-mutation is attested from 1874; earlier was i-umlaut (1869), from German.
mutatis mutandis: "with the necessary changes," Latin, literally "things being changed that have to be changed," from the ablative plurals of, respectively, the past participle and gerundive of mutare "to change" (see mutable).
mute (adj.): late 14c., mewet "silent," from Old French muet "dumb, mute" (12c.), diminutive of mut, mo, from Latin mutus "silent, speechless, dumb," probably from imitative base *meue- (source also of Sanskrit mukah "dumb," Greek myein "to be shut," of the mouth). Form assimilated in 16c. to Latin mutus.
mute (v.): "deaden the sound of," 1861, from mute (n.). Related: Muted; muting.
mute (n.): 1570s, "stage actor in a dumb show;" 1610s as "person who does not speak," from mute (adj.). Musical sense first recorded 1811 of stringed instruments, 1841, of horns.