ardor vs doubt

ardor

noun
  • Intense heat. 

  • Great warmth of feeling; fervor; passion. 

  • Spirit; enthusiasm; passion. 

doubt

verb
  • To be undecided about; to lack confidence in; to disbelieve, to question. 

noun
  • Disbelief or uncertainty (about something); (countable) a particular instance of such disbelief or uncertainty. 

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