Azrael vs pale rider

Azrael

name

  • The angel of death in Catholic and Orthodox Christianity, and in Islam. 

pale rider

noun

  • Death, the Grim Reaper or angel of death; and one of the Four Horsemen of the Apocalypse. 

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