doubtfulness vs probability

doubtfulness

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

probability

noun
  • The state of being probable; likelihood. 

  • A number, between 0 and 1, expressing the precise likelihood of an event happening. 

  • An event that is likely to occur. 

  • The relative likelihood of an event happening. 

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