My husband, who spends his working life in the (English) Civil War year of 1645 (he works in a living history museum) explains "bumf" as "bumfodder" at that time, so it's an older term than the OED might suggest - the staff at the museum have got some written source for it in around 1650.

"Trolleys" is another word used (certainly locally) for male underwear. As well as a shopping cart. No, we don't get confused - context is everything.