Green’s Dictionary of Slang

(orig. US) a pistol.

1855		W.G. Simms Forayers 170: The pistols, Carrie, the old dogs!
1928		C. McKay Home to Harlem 287: Guess Billy is right toting his silent dawg around with him.
1949		L. Hughes Tambourines to Glory I vii: I carried a pistol, called it Dog.
2017		67 Beats Cypher‘’ 🎵 44 let me dog bark (drill it drill it drill it) / I said 44 let me dog bark.