Green’s Dictionary of Slang

goof pill n.

also goofy
[var. goofball n.1 (2)]

(drugs) a barbiturate.

Show quotations
[US]Mencken Amer. Lang. Supplement II 682: A sodium pentobarbital capsule is a goof-pill.
[Scot](con. mid-1960s) J. Patrick Glasgow Gang Observed 52: We came pourin’ oot, aw jazzed up in wir tin flutes, aw drunk and blocked up wi’ the goofies.