despot vs empress

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) 

empress

noun
  • The female monarch (ruler) of an empire. 

  • The third trump or major arcana card of most tarot decks. 

  • A female chimpanzee. 

  • A deciduous tree, Paulownia tomentosa 

  • The wife or widow of an emperor or equated ruler. 

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