Valhalla vs purgatory

Valhalla

name
  • The home of half of all warriors who died gloriously in battle as well as many of the Æsir. 

noun
  • An abode of the gods or afterlife in general. 

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 Valhalla and purgatory occurred in a corpus of books? (source: Google Ngram Viewer )