witch-hazel, n. — Green’s Dictionary of Slang

witch-hazel n.

[ext. of witch, the n.+ ref. to the light brown colour of much heroin; note hazel n.¹]

(drugs) heroin.

1936		D. Maurer ‘Argot of the Und. Narcotic Addict’ Pt 1 in AS XI:2 127/2: witch hazel. Heroin.
1959		J.E. Schmidt Narcotics Lingo and Lore 191: Witch hazel – Heroin.