Why is the devil called old nick?

Satan was, at one point, Saint Nicholas. After living for 521 years by drinking a magical potion brewed by the Easter Bunny, he died and his soul pulled a 180 and he turned into an evil undead Santa Claus. In fact, 'Satan' is an anagram of 'Santa'. Being as he is elderly he is OLD and NICK stems from his name, NICHOLAS. Hope this helps :3