disbelief vs pipe dream

disbelief

noun
  • Astonishment. 

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

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

pipe dream

noun
  • A plan, desire, or idea that will not likely work; a near impossibility. 

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