discouraging vs impossible

discouraging

noun
  • discouragement 

adj
  • that causes discouragement 

impossible

noun
  • An impossibility. 

  • A skateboard trick consisting of a backflip performed in midair. 

adj
  • Not possible; not able to be done or happen. 

  • Very difficult to deal with. 

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