Green’s Dictionary of Slang

(mainly juv.) to remove someone’s trousers whether they like it or not.

1945		in G. Legman Limerick (1953) 339: He’d catch something neat / In a Pullman retreat, / Say ‘How do you do?’ and then pants it.
1993		M. Myers et al. Wayne’s World II [film script] Garth: Who pantsed me at the tenth grade assembly in front of the world.