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gow (n.)[gow 词源字典]: 1915, "opium," from Cantonese yao-kao "opium," literally "drug-sap;" used as such by Raymond Chandler, etc.; by 1950s the meaning had expanded to "pictures of nude or scantily clad women," hence gow job "flashy girl," which in teenager slang came to also mean "hot rod."[gow etymology, gow origin, 英语词源]
hot-rod (n.): also hot rod, 1945, American English, from hot + rod, apparently in a sense of "hunk of metal" (the cars also were called hot iron).
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.