constancy vs devotion

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. 

devotion

noun
  • Feeling of strong or fervent affection; dedication 

  • The act or state of devoting or being devoted. 

  • Religious veneration, zeal, or piety. 

  • A prayer (often found in the plural) 

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