apathetic vs single-hearted

apathetic

adj
  • Void of feeling; not susceptible of deep emotion. 

  • Of, or pertaining to apatheism. 

single-hearted

adj
  • Having an honest heart; straightforward, free from duplicity. 

  • Devoted; unambivalent and dedicated. 

How often have the words apathetic and single-hearted occurred in a corpus of books? (source: Google Ngram Viewer )