myriarchy vs novemvirate

myriarchy

noun
  • An area controlled by a Mongolian myriarch and theoretically comprising 10,000 households. 

  • A regiment of 10,000 soldiers, especially (historical) a Mongolian toman. 

novemvirate

noun
  • A group of nine people, especially (politics) a council of nine men who share office or rule. 

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