1944, from bebop, rebop, bop, nonsense words in jazz lyrics, attested from at least 1928. The style is associated with Charlie Parker and Dizzy Gillespie.
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."