dictator vs overlord

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. 

overlord

noun
  • A ruler of other rulers. 

  • A feudal lord directly owed rent or personal service by a tenant of subinfeudated land, a tenant's liege lord. 

  • Anyone with overarching power or authority in a given domain. 

verb
  • To rule over; to domineer. 

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