Green’s Dictionary of Slang

(drugs) amyl nitrite, isobutyl nitrite.

1969		R.R. Lingeman Drugs from A to Z (1970) 31: amys, also called pearls and snappers. Small glass vials containing amyl nitrite.
1972		B. Rodgers Queens’ Vernacular.
1981		D.E. Miller Bk of Jargon 338: snappers: Amyl nitrite.
2001		ONDCP Street Terms 19: Snappers — Isobutyl nitrite.