disbelief vs doubtfulness

disbelief

noun
  • Unpreparedness, unwillingness, or inability to believe that something is the case. 

  • Astonishment. 

  • The loss or abandonment of a belief; cessation of belief. 

doubtfulness

noun
  • The state or quality of being doubtful; doubt; uncertainty. 

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