Abaddon vs Avernus

Abaddon

name
  • Hell; the bottomless pit; a place of destruction. 

  • The destroyer, or angel of the bottomless pit; Apollyon; 

Avernus

name
  • The entrance to Hell or the underworld, or the underworld itself. 

  • A lake in Southern Italy. 

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