Green’s Dictionary of Slang

(US) an alcoholic tramp; thus as a nickname.

1948		W. O’Sullivan ‘Killer’s Cue’ in Range Riders Western Jan. 🌐 Bummy Rhoades, bewhiskered, tobacco-chewing, horny-handed son of toil and mirth and the roofless spaces.
1949		N. Algren Man with the Golden Arm 24: Where he got it only the blind bummy called Pig [...] might have guessed.
1956		N. Algren Walk on the Wild Side 80: The first place he saw where beggars and bummies can lie down to rest.
1990		S. Morgan Homeboy 41: Beggars, bummies and bindlestiffs of every bent.