Etymology
Advertisement
muscle (n.)

"contractible animal tissue consisting of bundles of fibers," late 14c., "a muscle of the body," from Latin musculus "a muscle," literally "a 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 combining 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;" Cornish logodenfer "calf of the leg," literally "mouse of the leg." 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 "muscle, strength, brawn" is by 1850; that of "force, violence, threat of violence" is 1930, American English. Muscle car "hot rod" is from 1969.

Related entries & more 
Advertisement
muscle (v.)

1913, "to accomplish by strength," from muscle (n.). Meaning "coerce by violence or pressure" is by 1929 in U.S. underworld slang. Related: Muscled; muscling.

Related entries & more 
muscle-bound (adj.)
1879, from muscle (n.) + bound, past participle of bind (v.).
Related entries & more 
muscle-man (n.)

1929, originally "an underworld enforcer;" sense of "strong man" is attested by 1952; from muscle (n.) + man (n.).

Related entries & more 
muscled (adj.)
"having muscles (of a particular type)," 1640s, from muscle (n.).
Related entries & more 
Advertisement
intramuscular (adj.)
also intra-muscular, 1874, from intra- "within" + muscle (Latin musculus) + -ar.
Related entries & more 
muscly (adj.)

"exhibiting great muscular development," 1590s, from muscle (n.) + -y (2).

Related entries & more 
musculature (n.)

"system of muscles considered with reference to its origin and development," 1875, from French musculature, from Latin musculus (see muscle (n.)).

Related entries & more 
musculo- 
word-forming element meaning "involving or pertaining to muscles," from combining form of Latin musculus "muscle" (see muscle (n.)).
Related entries & more 
myo- 
before vowels my-, word-forming element meaning "muscle," from combining form of Greek mys "muscle," literally "mouse" (see muscle (n.)).
Related entries & more