Green’s Dictionary of Slang

1. a lavatory, usu. in a prison cell.

1942		Berrey & Van den Bark Amer. Thes. Sl.
1949		Monteleone Criminal Sl. (rev. edn) 108: growler A chamber pot used in a cell.
1975		G. Underwood ‘Razorback Sl.’ in AS L:1/2 60: growlern Toilet.

2. a prison.

1981

R. Graziano Somebody Down Here Likes Me, Too 136: The police take ’im in for a night in the growler.