Professor vs sachem

Professor

noun
  • The title for someone who holds the professor job. 

sachem

noun
  • A boss, a leader. 

  • A chief of one or several Native American tribe(s), especially of the Algonquians; a sagamore. 

  • A high-ranking officer of the Tammany Hall political organization. 

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