eternal sleep vs pale rider

eternal sleep

noun
  • Death 

  • A magical state of suspended animation, a state of ageless, deathless, everlasting sleep. Well-known examples are Endymion, (the lover of the Greek moon goddess, Selene), and the princess from Sleeping Beauty. 

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 eternal sleep and pale rider occurred in a corpus of books? (source: Google Ngram Viewer )