constancy vs intermittence

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. 

intermittence

noun
  • The state of being sporadic or intermittent; a lack of flow or fluency. 

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