napper vs wetback

napper

noun
  • The head. 

  • A person who takes a nap. 

wetback

noun
  • A person of the mestizo race; a mojado. 

  • A Mexican or Central American who illegally enters the United States of America from its southern border. 

How often have the words napper and wetback occurred in a corpus of books? (source: Google Ngram Viewer )