Green’s Dictionary of Slang

an excl. of derision or annoyance.

1942		P. Larkin letter 20 Aug. in Thwaite Sel. Letters (1992) 43: After cautious fencing, Mrs G [...] & I have begun to swear. I say sod, bugger, bloody, and balls. She says bugger, bloody and bum.
1946		K. Amis letter 25 Feb. in Leader (2000) 46: I think you ought to see her. So ought I, come to that. Bum to that.
1959		D. Hewett Bobbin Up (1961) 42: ‘You’ll get your fingers caught in there one of these days. Then you’ll have something to squawk about.’ ‘Ah bum!’.
1964		P. White Burnt Ones 126: ‘Bum to you!’ Lova said.
1970		H.E. Bates A Little of What You Fancy (1985) 484: ‘Bum!’ Pop said very loudly from the bed.
1989		A. Ahlberg Heard it in the Playground (1991) 100: ... Bum!
1996		Penguin Bk of More Aus. Jokes 435: He’s got a spare. But what he doesn’t have is a jack. Bum, bum, bum.
2006		D. Mitchell Black Swan Green 80: ‘Oh, bum,’ I said.