doubtfulness vs vagueness

doubtfulness

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

vagueness

noun
  • The condition of being unclear; vague. 

  • Something which is vague, or an instance or example of vagueness. 

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