ardor vs inconstancy

ardor

noun
  • Spirit; enthusiasm; passion. 

  • Intense heat. 

  • Great warmth of feeling; fervor; passion. 

inconstancy

noun
  • Lack of constancy; lack of consistency in thought, emotion or action. 

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