Green’s Dictionary of Slang

(drugs) opium.

1933		Ersine Und. and Prison Sl.
1942		Berrey & Van den Bark Amer. Thes. Sl.
1953		Anslinger & Tompkins Traffic In Narcotics 314: pox. An opium pill. Also a ration of opium prepared for smoking.
1959		J.E. Schmidt Narcotics Lingo and Lore.
2001		ONDCP Street Terms 17: Pox — Opium.