novemvirate vs quinquevirate

novemvirate

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

quinquevirate

noun
  • An official group of five people, especially a council of five men sharing office or rule. 

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