Green’s Dictionary of Slang

stylish, up-to-date.

1921		N.Y. Tribune 4 Sept. 47/5: The Jazzbo Jubilators [...] arrive at the laboratory to record ‘The Bathhouse Blues’.
1928		R. Carr Rampant Age 98: Polkadot shirts and small, violent, ‘jazz-bow’ neckties.
1950		J.T. Farrell ‘Willie Collins’ in Amer. Dream Girl (1950) 214: A recently purchased polka-dot jazzbo tie.