leadership vs quinquevirate

leadership

noun
  • A group of leaders. 

  • The capacity of someone to lead others. 

  • The office or status of a leader. 

quinquevirate

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

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