I heard a very interesting radio programme today, discussing this subject - here is the website in case you are interested:
http://www.bbc.co.uk/routesofenglish/index.shtml

The premise of the section that I heard was that the popularity of a swear word had a lot to do with its sound. To be very effective it had to sound like a punch, and short vowels make “punchier” words. Some consonants have “explosive” sounds making them particularly effective – try saying “f” or “c” – they can sound quite aggressive.

Billy Connolly said that in order to avoid swearing in front of his children he made up quite believable swear words using these principles. Think of the difference between calling someone a “rat”, rather than a “mouse” – a rat would sound more aggressive, even if you knew nothing about the animal.

The other interesting area was how much movement there was over the words. “Rabbit” was brought in to replace the word “coney” which had gained a rather course usage. Many words become more acceptable over the years - few of us would be all that offended by most Shakespearian insults - new words are found to take their places.