Green’s Dictionary of Slang

1. (US campus) the penis.

1967–8		Baker et al. CUSS.
1972		B. Rodgers Queens’ Vernacular.

2. (US black) a gun.

1975

N. De Mille Smack Man (1991) 19: His puppy was the long-barrel .45, also called a yeng, a gong, or a tool.