cecil, n.¹ — Green’s Dictionary of Slang

cecil n.¹

[Spears, Slang and Jargon of Drugs and Drink (1986), suggests a play on M. sul., morphine sulphate]

(US drugs) morphine.

1933		Ersine Und. and Prison Sl.
1942		Berrey & Van den Bark Amer. Thes. Sl.
1950		Goldin et al. DAUL 41/2: Cecil. Morphine.