kangaroo court vs tribunal

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. 

tribunal

noun
  • An assembly including one or more judges to conduct judicial business; a court of law. 

  • A kind of village hall used to transact business, to quarter troops and travellers, and to confine prisoners. 

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