fiendish vs ghoulish

fiendish

adj
  • Sinister; evil; like a fiend. 

  • Very difficult. 

ghoulish

adj
  • Of or pertaining to corpses and graverobbing. 

  • Of or pertaining to ghouls. 

  • Fascinated by corpses. 

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