captor vs guardian

captor

noun
  • One who is holding a captive or captives. 

  • One who catches or has caught or captured something or someone. 

guardian

noun
  • Someone who guards, watches over, or protects. 

  • A superior in a Franciscan monastery. 

  • A person legally responsible for a minor (in loco parentis). 

  • A person legally responsible for an incompetent person. 

  • A major or final enemy; boss. 

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