kangaroo court vs magistracy

kangaroo court

noun
  • A judicial or quasi-judicial proceeding, or a group of people which conducts such proceedings, which is without proper authority, and often acts abusively or decides unjustly. 

magistracy

noun
  • The collective body of magistrates. 

  • The dignity or office of a magistrate. 

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