There's a noted chemist named Warren Warren. Washington State had a football player named Samoa Samoa. Hawaii had a great volleyball player named Allen Allen.
The beat goes on. ;-)
The beat goes on. ;-)
Near-miss: the poet William Carlos Williams.
He also graduated from the University of Walla Walla.
You might call them Bill, but they can decide to call themselves Billy, or Will, or Willy, or William - without the hassle of actually changing their name.
There is also a class thing where naming a kid with a short form is seen as being lower class.