The word 'werewolf' comes from the Old English words 'wer', meaning 'human male' and 'wulf' meaning 'wolf'.  Almost all world cultures have folk tales concerning the shapeshifting of animals into humans, and in Europe the concept of the werewolf is the most enduring.  A myriad of tales usually asserted that a person was transformed into one of these creatures in order to serve the Devil, and subsequently there are parallels to the accusations of witchcraft and vampirism which abounded throughout Europe for centuries.  It is interesting to note that there were fewer stories from England, probably due to the fact that the wolf population had been extinguished by the Anglo-Saxons (though the myth of the 'black dog' was, and is, very well known). 

A huge number of novels, TV Series and films have been written or made about werewolves, demonstrating their power as both a symbol of brute masculinity and a source of fear. 

Excellent werewolf resources website.