Clipping of barbiturate + -ie (diminutive suffix).
Meanings
(informal) A barbiturate.
Then one day the King said, / Jules, you're grounded. / Absolutely grounded. / This is it. So Jules took / barbies, you know, barbiturates, / and he stayed down. Way down. / Grounded like his father said. 1989, The Pembroke Magazine, volumes 21–23, page 162:
“At nights,” she says, “we were both in our own little worlds, him with his alcohol and me with my barbies.” 1971, The Bulletin, volume 93, numbers 4762–4774, page 35: