reign of terror vs tyranny

reign of terror

noun
  • A period of brutal intimidation and violence by those in power. 

tyranny

noun
  • A government in which a single ruler (a tyrant) has absolute power; this system of government. 

  • The office or jurisdiction of an absolute ruler. 

  • Extreme severity or rigour. 

  • Absolute power, or its use. 

  • A system of government in which power is exercised on behalf of the ruler or ruling class, without regard to the wishes of the governed. 

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