elector vs emperor

elector

noun
  • A person eligible to vote in an election; a member of an electorate, a voter. 

  • A member of an electoral college; specifically (US) an official selected by a state as a member of the Electoral College to elect the president and vice president of the United States. 

  • A person eligible to vote to elect a Member of Parliament. 

emperor

noun
  • A large, relatively valuable marble in children's games. 

  • Any of various butterflies of the subfamily Charaxinae. 

  • Specifically, the ruler of the Holy Roman Empire; the world-monarch. 

  • Any of various large dragonflies of the cosmopolitan genus Anax. 

  • An emperor penguin. 

  • The fourth trump or major arcana card of the tarot deck. 

  • The male monarch or ruler of an empire. 

  • Any monarch ruling an empire, irrespective of gender, with "empress" contrasting to mean the consort of an emperor. 

  • Any fish of the family Lethrinidae. 

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