guardian vs shielder

guardian

noun
  • A superior in a Franciscan monastery. 

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

  • A person legally responsible for an incompetent person. 

  • Someone who guards, watches over, or protects. 

  • A major or final enemy; boss. 

shielder

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