magistracy vs supervision

magistracy

noun
  • The dignity or office of a magistrate. 

  • The collective body of magistrates. 

supervision

noun
  • The act or instance of supervising. 

  • A tutorial session for an individual student or a small group. 

  • Responsible oversight. 

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