illegal alien vs squatter

illegal alien

noun
  • A person who is within the boundaries of a political state without the authorization of the government of that state; a national of another country who has entered or stayed without permission. 

squatter

noun
  • A poor vagrant; An illegal informal settler; hobo; beggar; One suffering from extreme poverty. 

  • One who occupied Crown land. 

  • A large-scale grazier and landowner. 

  • One who squats, sits down idly. 

  • A squat toilet. 

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