autocracy vs undecimvirate

autocracy

noun
  • A form of government in which unlimited power is held by a single individual. 

  • An instance of this government. 

undecimvirate

noun
  • A group of eleven people, especially (politics) a council of eleven men sharing office or power and particularly (historical) the groups of eleven magistrates in ancient Athens. 

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