Green’s Dictionary of Slang

gonga n.¹

(US prison) marijuana.

1935		implied in gonga smudge
1956		(con. 1940s) J. Resko Reprieve 236: The raw, fresh leaves of marijuana, gage, mota, gonga, griffo, tea, weed [...] are packed loosely in a small sized tobacco tin.
1992		Bentley & Corbett Prison Sl. 71: Smoke Marijuana. (Archaic: yen-pop, gonga).

In compounds

gonga smudge (n.)

(US Und.) a marijuana cigarette.

1935

A.J. Pollock Und. Speaks n.p.: Gonga smudge, a marijuana cigarette.