demonly vs fiendish

demonly

adj

  • Of, relating to, or like a demon; demonic. 

adv

  • In a manner befitting or like a demon. 

fiendish

adj

  • Sinister; evil; like a fiend. 

  • Very difficult. 

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