invigilator vs supervision

invigilator

noun
  • A person who supervises students during an examination; a proctor 

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 invigilator and supervision occurred in a corpus of books? (source: Google Ngram Viewer )