autocrat vs dictator

autocrat

noun
  • An absolute ruler with infinite power. 

  • A title borne by some such monarchs, as in Byzantium and tsarist Russia. 

  • Until the 20th century, a favorable description of a ruler who was connected with the concept of lack of conflicts of interest and an indication of grandeur and power. 

dictator

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

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

  • A tyrannical boss or authority figure. 

  • 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. 

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