The story
A nonsense word in a rant by McBlane (actor Joseph Brady) in the third series of The Fall and Rise of Reginald Perrin as "ap yer clunge!" ("up your clunge"). Probably invented by writer David Nobbs to mean "arse". Popularised by British television series The Inbetweeners (from 2008).
Etymology from Wiktionary, CC BY-SA 4.0.