knucklehead vs squarehead

knucklehead

noun
  • An idiot; a stupid or inept person. 

squarehead

noun
  • A socially conventional or boring person. 

  • A foreigner of Germanic origin, especially a German, Dutch, or Scandinavian person. 

  • An honest person; a non-criminal. 

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