Green’s Dictionary of Slang

a belch.

1932		J.L. Kuethe ‘Johns Hopkins Jargon’ in AS VII:5 330: burp [...] n. —sound made when belching.
1939		New Masses 28 Feb. 28: It was so chastely devised that Brother Will Hays blessed it without a burp.
1941		C. Sandburg letter 24 Mar. in Mitgang (1968) 404: We knew it when it was in swaddling clothes and had a bib for its burps.
1952		W.R. Burnett Little Men, Big World 56: It gave a loud belch. Arky started slightly and stared at the baby in disapproving surprise. ‘Oh, nice burp for Aunt Anna.’.
1965		J.P. Carstairs Concrete Kimono 9: Pardon the burp.
1970		H.E. Bates A Little of What You Fancy (1985) 442: Ma [...] urged him to have another good burp or two.
1989		A. Ahlberg Heard it in the Playground (1991) 24: Then: a noise like an angry burp.
2000		J. Stevenson London Bridges (2001) 155: I put all I got into Eugenides’ burp mixture.
2006		I. Rankin Naming of the Dead (2007) 375: ‘It’s me she wants to take on,’ Keith Carberry called out, stifling a burp.
2011		S. Kelman Pigeon English 67: It made my burps taste like burning.