overman vs superman

overman

noun
  • A person with great powers; a superman. 

  • A person who supervises others; a supervisor, especially in a mine. 

verb
  • To provide with too many personnel; overstaff. 

superman

noun
  • A man of extraordinary or seemingly superhuman powers. 

  • An imagined superior type of human being representing a new stage of human development; an übermensch, an overman. 

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