Bop
1940s: shortening of bebop.
wiktionary
Imitative of the sound made.
Shortened from bebop.
etymonline
bop (n.)
1948, shortening of bebop or rebop. The musical movement had its own lingo, which was in vogue in U.S. early 1950s. "Life" magazine [Sept. 29, 1952] listed examples of bop talk: crazy "new, wonderful, wildly exciting;" gone (adj.) "the tops--superlative of crazy;" cool (adj.) "tasty, pretty;" goof "to blow a wrong note or make a mistake;" hipster "modern version of hepcat;" dig "to understand, appreciate the subtleties of;" stoned "drunk, captivated, ecstatic, sent out of this world;" flip (v.) "to react enthusiastically."
bop (v.)
"to hit, strike, punch," 1931, imitative. As a noun from 1934. Sense of "play bop music, play (a song) in a bop style" is from 1948, from bop (n.). It soon came to mean "do any sort of dance to pop music" (1956). Related: Bopped; bopping.