bung, n.⁵ — Green’s Dictionary of Slang

bung n.⁵

[ety. unknown; ? bung v.¹ (3), i.e. it ‘throws away’ the truth]

(UK juv.) a lie.

1882		A.M. Brookfield Autobiog. Thomas Allen I 61: ‘And for having told a bung,’ said Fisher. ‘A beastly bung,’ cried all the judges .
1902		H. Baumann Londinismen (2nd edn).
1913		M. Baring Lost Diaries 8: Mac reported him for telling bungs. He wasn’t swished as its his first term .