guardianship vs supervision

guardianship

noun
  • The office or position of one acting as a guardian or conservator, especially in a legal capacity. 

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