constancy vs dirty trick

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. 

dirty trick

noun
  • Unethical or illegal tactics used against an opponent. 

  • An unkind trick. 

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