cosigner vs guardian

cosigner

noun
  • A person who accepts joint responsibility for the debt of another 

  • A cosignatory 

guardian

noun
  • A person legally responsible for an incompetent person. 

  • A superior in a Franciscan monastery. 

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

  • Someone who guards, watches over, or protects. 

  • A major or final enemy; boss. 

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