Green’s Dictionary of Slang

nonsense! rubbish!

1902		Minneapolis Jrnl (MN) 6 Sept. 4/3: The enterprising New York Sun [...] pleads for a thesaurus of fine old English and American ‘cuss words’ [...] such beloved ejaculations as ‘Oh, pants!’ ‘I’ll be hornswoggled,’ ‘I’ll be dingswizzled!’.
1997		Roger’s Profanisaurus in Viz 87 Dec. n.p.: pants 1. interj. Exclamation of dismay. 2. n. Rubbish; nonsense; arse. As in: ‘You’re talking pants!’.