DOOM Anomaly

Swearwords, as Quast said, have quite a history behind them. Usually in the days of old, some of them would be a way to call upon the powers of Evil and was considered to be blasphemy to utter.

It also differs from language to language I'd assume, but many swearwords have an old meaning to them and back when they were "invented", you can bet your socks that it would've been among the most terrible things to say.

On a related note, it's rather funny how formerly so acceptable words become taboo.
"Retard" for instance (disregarding its overfrequent use on the internet), is considered an insult nowadays, while back in the day it was a perfectly acceptable term to denote a physically handicapped person.
I remember that I told my parents about the word "retard" and they were damn surprised that it had evolved into an insulting word :-P

Moreover, you can't use the word "retard" as describing "to slow or inhibit" because someone's bound to take offense.

I remember the orthodontist telling me that some of my teeth were retarding the growth of others.

Also, it's pretty stupid that crazy femynists claim that vagina is a vulgar word because it means 'sheath' and cunt should be the proper word because it means 'flower' or somesuch. According to that article, they are completely wrong.