Green’s Dictionary of Slang

a general term of disdain, usu. only used by children.

1903		L.A. Times 24 May 11/7: ‘When Bumface Schneider came up they pasased him along to the morgue’.
1948		K. Amis letter 12 Jan. in Leader (2000) 155: I had an impudent letter from Caton (perhaps I told you) asking me to call on him and ‘report sales’ the BUMFACE the bumface.
1986		P. Slabolepszy ‘Boo to the Moon’ in Mooi Street (1994) 114: How’s ou bum-face?
1986		T. Winton That Eye, The Sky 34: Piss off, bumface.
1998		Guardian 4 July 51/1: ‘In your dreams, bum-face’.
2001		Guardian Education 13 Mar. 44/1: ‘Is that you Bumface [...] You’re still the same bossy Bumface’.