duck soup vs impossible

duck soup

noun
  • Used other than figuratively or idiomatically: see duck, soup. 

  • Something which is easy; a piece of cake. 

impossible

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

  • Very difficult to deal with. 

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

  • An impossibility. 

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