Green’s Dictionary of Slang

hache n.

[Sp. hache, the letter H]

(drugs) heroin.

1955		H. Braddy ‘Narcotic Argot Along the Mexichailan Border’ in AS XXX:2 87: HACHE (Sp. pronunciation of the letter H), n. Heroin.
2001		ONDCP Street Terms 11: Hache — Heroin.