history of curse words

I've been thinking about the history of curse words ever since starting to watch the British teen show Skins. The show has tons of drug use, sexual innuendo, profanity, etc. However, much of it goes over my head, either because I cannot understand what they're saying because of the accent (and talking quickly) or because I have no idea what the word means. urbandictionary.com is now one of my more frequently visited sites.

- disclaimer: the show is really well done and i'm learning a lot about British teen culture. however, I wouldn't recommend it to everyone.

Looking up the wikipedia article on profanity was interesting. I think it's fascinating that we use curse words only for certain subjects: the supernatural, body functions and organs, disease & death, sexuality, disfavored people or groups (this is according to Steven Pinker's book The Stuff of Thought)

I wonder why...