=D In some places like UK "bum" is a slang to say butt. So I guess what you've learned applies here too ^^

Yeah, "me bum" is more UK/Australian slang than US but it's slang. "me" is improper English for "my" used rather often in the UK/Australia The word "bum" can mean more than just "butt/backside" depending on usage. Example: "Can I bum a dollar from you?" In that case it's like. "get"/"have"/"borrow" It's like the person who is asking the question is comparing themselves to a homeless person or a "bum" and implying that they are poor; therefore, they need a dollar. Understand? I hope I'm not confusing you. ~ Anyway, to really answer your question it is slang for "I'm very busy" It's saying that they are sooo busy that they can't scratch their own backside.

Educated Australians don't say "me bum" , they say "my behind" or "I'm so busy, that I don't have time to scratch myself"

I agree with Sarah and Ria, it's a dialectical difference. Plus, the more crass a subject is, the more words/euphemisms we use for it. ;) As an Aussie, I'd use backside, bum, arse or clacker (my fav, very "educated" Australian, heh), but not tush, heinie, ass or butt - other people would use those. As for "me" it's ease of pronunciation. I think "m-ee" is much easier to say than the grammatically correct "m-a-i". So you'll sometimes hear "me" said in place of "my": me mates, me car, me beer...

pirate dialect.^^