why Americans always sound stupid when they try to use British slang

I keep my Facebook set to UK English partly because, as a British lit specialist, I find extra u’s oddly comforting, and partly because then I learn things like the fact that “pigeonhole” is apparently British slang for a cubbyhole-style mailbox.

I had fleeting dreams of telling my students to leave things in my pigeonhole, but then I saw that Wikipedia tells me that I can also call it a pidge.  That’s even better. 

The problem, though, is that in America, “just put it in my pidge” sounds dirty as all hell.