risible vs unfunny

risible

adj
  • Provoking laughter; ludicrous; ridiculous; humorously insignificant 

  • Easily laughing; prone to laughter 

  • Of or pertaining to laughter 

unfunny

adj
  • Not funny, especially when attempting to be. 

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