Avalon vs purgatory

Avalon

name
  • An island, represented as an earthly paradise in the western seas, to which King Arthur and other heroes were carried at death. 

  • A city in Los Angeles County, California, United States, on the island of Catalina. 

purgatory

noun
  • Any situation where suffering is endured, particularly as part of a process of redemption. 

adj
  • Tending to cleanse; expiatory. 

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