Panties & scanties

Were men's pants (slacks) ever called "panties"? I was watching a DVD of an old movie, "42nd Street" with Ruby Keeler and Dick Powell. Mr. Powell was singing to Ms. Keeler:

Shuffle Off to Buffalo
Written by Al Dubin (lyrics) and Harry Warren (music) in 1932 for "42nd Street."

.I'll go home and get my panties
You go home and get your scanties
And away we'll go;
Mm, off we're going to shuffle,
Shuffle off to Buffalo

My guess is that it's just 'poetic licence' and merely used to for rhyming purposes. I've been around almost since 1932 and I've never heard men's trousers called 'panties' - these are ALWAYS female items! Mark you, 'pants' in the UK are not trousers, but 'underpants' - 'unterhosen' in German, which is my bet where the US usage came from.