Well - this one's not slang, but a swearing story. When I was younger, seven or eight or so, my mates and I thought we would be very clever and call people asses in a secret way. So that our parents, teachers, and other adults wouldn't catch on, yeah? We'd learned the Hebrew word for donkey, and so for a summer it was My brother's being an ayir today and Don't be such an ayir, Bill. Problem was, of course, that the way we were using it made it clear how the word was meant, even for the teachers who had no idea what we were on about - and our parents all caught on because they knew the word. My dad thought it was hilarious, and he encouraged it, but some of the others got smacks for their trouble.