Why was his nickname 'Buster'?

After Buster Keeton. Google the name if you're too young to know him. :)

Yes bc his last name is Keeton- they call him Buster for Buster Keeton who was a famous silent film star. He was like Charlie Chaplin and they both did silent films way back in the early part of the century. If you've seen the movie "Benny and Joon" there is a reference to him when Johnny Depp is reading a book about him on the train. Depp's character was trying to copy him.