decemvirate vs executive branch

decemvirate

noun
  • A group of ten people, especially (politics) a council of ten men sharing office or power and particularly (historical) the groups of ten men who reformed and codified Roman law circa 450 BCE. 

executive branch

noun
  • The branch of government that oversees the carrying out of the laws 

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