Green’s Dictionary of Slang

(US) that’s disgusting! don’t make me sick!

1975		G. Underwood ‘Razorback Sl.’ in AS L:1/2 56: barf [...] 2: interj A term of disapproval or disgust.
1976		P. Conroy Great Santini (1977) 317: ‘A man in my position has to be pretty selective.’ ‘Oh barf,’ Mary Anne said.
1990		T. Winton Human Torpedo 81: In a school full of [...] Kylie Minogues (barf!).
2004		P. Howard PS, I Scored the Bridesmaids 207: ‘Srha cant find out but I thnk Im in lov wth hm.’ Barf!