Green’s Dictionary of Slang

jimmy dog n.

[ety. unknown]

1. (Irish juv.) the penis.

[Ire]Share Slanguage.

2. (US campus) a marijuana cigarette.

[US]Eble Campus Sl. Oct.
[US]Eble Sl. and Sociability 70: Dog is often the second member of a compound or phrase: [...] hooch dog, jimmy dog, james earl dog ‘marijuana cigarette’.