"flesh of sheep used as food," c. 1300, mouton (c. 1200 as a surname), from Old French moton "mutton; ram, wether, sheep" (12c., Modern French mouton), from Medieval Latin multonem (8c.), probably [OED] from Gallo-Roman *multo-s, accusative of Celtic *multo "sheep" (source also of Old Irish molt "wether," Mid-Breton mout, Welsh mollt), which is perhaps from PIE root *mel- (1) "soft."
The same word also was borrowed into Italian as montone "a sheep," and mutton in Middle English also could mean "a sheep" (early 14c.). 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 "cut of mutton (usually containing a rib) for cooking" is from 1720; as a style of side whiskers from 1865, so called for the shape (narrow and prolonged at one end and rounded at the other).
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 is by 1917 in reference to "a pair of stupid men, affable losers," or to one tall (Mutt) and one short (Jeff), from the comic strip characters from the heyday of the newspaper funny pages, Augustus Mutt and Jim Jeffries, in U.S. cartoonist Henry Conway ("Bud") Fisher's strip, which debuted in 1907.
ruminant mammal, Old English sceap, scep, from West Germanic *skæpan (source also of Old Saxon scap, Old Frisian skep, Middle Low German schap, Middle Dutch scaep, Dutch schaap, Old High German scaf, German Schaf), of unknown origin. Not found in Scandinavian (Danish has faar for "sheep") or Gothic (which uses lamb), and with no known cognates outside Germanic. The more usual Indo-European word for the animal is represented in English by ewe.
The plural form was leveled with the singular in Old English, but Old Northumbrian had a plural scipo. Used since Old English as a type of timidity and figuratively of those under the guidance of God. The meaning "stupid, timid person" is attested from 1540s. The image of the wolf in sheep's clothing was in Old English (from Matthew vii.15); that of separating the sheep from the goats is from Matthew xxv.33. To count sheep in a bid to induce sleep is recorded from 1854 but seems not to have been commonly written about until 1870s. It might simply be a type of a tedious activity, but an account of shepherd life from Australia from 1849 ["Sidney's Emigrant's Journal"] describes the night-shepherd ("hut-keeper") taking a count of the sheep regularly at the end of his shift to protect against being answerable for any animals later lost or killed.
Sheep's eyes "loving looks" is attested from 1520s (compare West Frisian skiepseach, Dutch schaapsoog, German Schafsauge). A sheep-biter was "a dog that worries sheep" (1540s); "a mutton-monger" (1590s); and "a whore-monger" (1610s, i.e. one who "chases mutton"); hence Shakespeare's sheep-biting "thieving, sneaky."
mid-14c., "act of chopping, cutting with a quick blow," from chop (v.1). Meaning "piece cut off" is mid-15c.; specifically "slice of mutton, lamb, or pork" (usually cut from the loin and containing the rib) is from 1630s, probably from being "chopped" from the loin. Sense of "a blow, strike" is from 1550s. Specific cricket/baseball sense of "a downward stroke with the bat" is by 1888.
1841 in cookery, reborrowing from French of the same word that had been taken 14c. and Englished as fillet (q.v.). Filet mignon (literally "dainty fillet") for "small, round, tender cut of meat from the center of the fillet" is attested as a French word in English from 1815.
The 'Chateaubriand,' the 'entrecôte,' and the 'filet mignon' (of mutton), with other forms, are all due to the more enlarged sympathies of the French butcher for what is perfect. We must entirely change the mode of cutting up the carcase before we can arrive at the same perfection in form of meat purchasable, and as that is hopeless, so is it useless to insist further on the subject on behalf of the public. ["The Kitchen and the Cellar," Quarterly Review, April 1877]