In other words,why Mike Judge named one of characters "Beavis"? Was there also some slang meaning or word play behind it as in "Butthead"?
There was a kid in Mike Judge's neighborhood when he was growing up named Bobby Beavis, according to him in this interview. A Google search of pre-1993 books will show many examples of people with that name. There was also a kid who called himself "Iron-Butt", and one of the other kids called him "Butt-Head".