Green’s Dictionary of Slang

gunny n.2

[abbr. gungeon n.]

(drugs) marijuana.

[US] ‘Sl. of Watts’ in Current Sl. III:2.
[US]O. Hawkins Ghetto Sketches 119: I don’t know where my head was, behind that jive wine and that bad gunny.
[US]E. Folb Runnin’ Down Some Lines 241: gunny Marijuana.