constancy vs unfaithfulness

constancy

noun
  • The quality of being constant; steadiness or faithfulness in action, affections, purpose, etc. 

  • An unchanging quality or characteristic of a person or thing. 

unfaithfulness

noun
  • The characteristic of being unfaithful; infidelity; disloyalty. 

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