 The term "bebop" is derived from nonsense syllables (vocables) used in scat singing; the first known example of "bebop" being used was in McKinney's Cotton Pickers' "Four or Five Times", recorded in 1928.It appears again in a 1936 recording of "I'se a Muggin'" by Jack Teagarden.A variation, "rebop", appears in several 1939 recordings.