Green’s Dictionary of Slang

(drugs) an injection of cocaine plus heroin or morphine.

1930		J. Tully Shadows of Men 211: When under the influence of a ‘whizbang,’ cocaine and morphine mixed together, he would ride millions of miles over endless valleys of snow.
1936		Mencken Amer. Lang. (4th edn) 579: The drug peddlers who began to flourish after the passage of the Harrison Act in 1915 were ready with neologisms to reinforce the terminology of drug addiction [...] A mixture of cocaine and morphine was called a whizz-bang.
1949		Monteleone Criminal Sl. (rev. edn).
1953		Anslinger & Tompkins Traffic In Narcotics 316: whiz-bang. A mixture of, or the injection of a mixture of cocaine, heroin, or morphine.
1966		R. Giallombardo Gloss. in Study of a Women’s Prison 209: Whizz Bang. A potent mixture of cocaine and morphine; any potent drug mixture.
2001		ONDCP Street Terms 22: Whiz bang — Cocaine; Heroin and cocaine.