discouraging vs doubtful

discouraging

adj
  • that causes discouragement 

noun
  • discouragement 

doubtful

adj
  • Subject to, or causing doubt. 

  • Experiencing or showing doubt, sceptical. 

  • Improbable or unlikely. 

  • Unclear or unreliable. 

  • Suspicious, or of dubious character. 

  • Undecided or of uncertain outcome. 

noun
  • A doubtful person or thing. 

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