devotion vs fervor

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) 

fervor

noun
  • An intense, heated emotion; passion, ardor. 

  • Heat. 

  • A passionate enthusiasm for some cause. 

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