Good Samaritan vs guardian angel

Good Samaritan

noun
  • A person who helps someone in distress. 

  • The subject of a particular New Testament parable. 

guardian angel

noun
  • A person who watches over another. 

  • A tutelary angel watching over a particular person in monotheistic contexts. 

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