diarchy vs tyranthood

diarchy

noun
  • A state under the rule of two people; the form of government of such state. 

  • Rule by two people. 

tyranthood

noun
  • The state or condition of being a tyrant. 

  • A governmental system based on a single ruler wielding absolute authority; tyranny. 

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