Green’s Dictionary of Slang

1. to remove someone’s trousers, either as a joke or as a form of punishment; thus n. debagging [post-1960s only in rare (public) school use].

1913		C. Mackenzie Sinister Street II 653: ‘We ought to debag him,’ he cried.
1917		A.S.G. Lee letter in No Parachute (1968) 8 Dec. 197: Three of us leapt on old Percy Wilcox from behind with the intention of debagging him.
1922		Joyce Ulysses 7: I don’t want to be debagged! Don’t you play the giddy ox with me!
1936		G. Greene Gun for Sale (1973) 173: Let’s get Watt and debag him.
1946		G. Gibson Enemy Coast Ahead (1955) 118: The barons [...] had begun to threaten the glamour boys that they would de-bag every one of them.
1953		P. Closterman (trans.) Big Show 89: A threat of public debagging [was] enough to calm him down.
1956		‘Charles Raven’ Und. Nights 15: After being caught, debagged, and ducked in a fountain.
1968		P. Barnes Ruling Class II iii: You debagged the Chaplain and hit the local constable over the head with an ebony shelalee.

2. in fig. use, to reveal the sexual underside.

1999

Guardian Guide 5–12 June 57: Graham Norton continues his debagging of popular culture.