imperator vs mikado

imperator

noun
  • An emperor. 

mikado

noun
  • Any emperor of Japan. 

  • A former title of the emperors of Japan during a certain period. 

  • A game of skill, in which identically shaped (but differently colored and valued) wooden sticks must be removed from a pile without disturbing the remaining stack. 

  • A fabric having a stiff twill weave. 

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