'barf' originates from American English, imitative (onomatopoeic) in origin, specifically early 20th century slang use of the sound 'barf' where the sound was intended to suggest retching or vomiting.

'barf' developed in colloquial American English in the early 1900s as an onomatopoeic slang term and moved from exclamatory/imitative uses into established verb and noun forms ('barf', 'barfed', 'barfing').

Initially it was an imitative exclamation suggesting retching; over time it became a standardized informal verb and noun meaning 'to vomit' or 'vomit'.