constancy vs vagary

constancy

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

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

vagary

noun
  • An impulsive or illogical desire; a caprice or whim. 

  • Something vague. 

  • An erratic, unpredictable occurrence or action. 

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