constancy vs unsteadiness

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. 

unsteadiness

noun
  • The quality of being unsteady. 

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