"to vomit or retch,"1960, American English slang, probably imitative. Related: Barfed; barfing. As a noun, from 1966. Barf bag "air sickness pouch" attested from 1966.
An exclamation of strong disgust: You want to know what I think of it? Barf! (1970s+)
[Computer 1980s+; probably echoic]