Green’s Dictionary of Slang

(US) a speakeasy or unlicensed drinking place.

1936		San Quentin Bulletin in L.A. Times 6 May 7: JINNY, a blind pig.
1949		Monteleone Criminal Sl. (rev. edn).
1950		Goldin et al. DAUL 110/2: Jinny. (Rural areas, South) A disreputable barroom, often link with prostitution.