dear heart vs sweetheart

dear heart

noun
  • Term of affection; sweetheart. 

sweetheart

noun
  • A person very much liked or loved by someone, especially when both partners are young. 

  • A person who is always very kind. 

  • A female member of a college or university fraternity. 

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