despot vs overlord

despot

noun
  • A ruler with absolute power; a tyrant. 

  • A title awarded to senior members of the imperial family in the late Byzantine Empire, and claimed by various independent or semi-autonomous rulers in the Balkans (12th to 15th centuries) 

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 despot and overlord occurred in a corpus of books? (source: Google Ngram Viewer )