demoniacal vs diabolical

demoniacal

adj
  • Pertaining to, characteristic of, or produced by a demon or evil spirit; devilish, demonic, fiendish. 

diabolical

adj
  • Of or concerning the devil; satanic. 

  • Extremely wicked or cruel. 

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