Green’s Dictionary of Slang

(drugs) narcotics.

1938		D. Maurer ‘Lang. of the Und. Narcotic Addict’ Pt 2 in Lang. Und. (1981) 101/1: cotics. Any kind of narcotics.
1942		Berrey & Van den Bark Amer. Thes. Sl.
1953		Anslinger & Tompkins Traffic In Narcotics 307: cotics. Narcotics.
1971		E.E. Landy Underground Dict. (1972).
2001		ONDCP Street Terms 6: Cotics — Heroin.