dictator vs grand vizier

dictator

noun
  • A tyrannical boss or authority figure. 

  • A person who dictates text (e.g. letters to a clerk). 

  • A totalitarian leader of a country, nation, or government. 

  • A magistrate without colleague in republican Ancient Rome, who held full executive authority for a term granted by the senate (legislature), typically to conduct a war. 

grand vizier

noun
  • A figure of great authority and power. 

  • The greatest minister of a sultan, with absolute power of attorney and, in principle, dismissable only by the sultan himself. 

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