happy hunting ground vs purgatory

happy hunting ground

noun
  • A Native American idea of the afterlife, conceived of as a paradise in which hunting is plentiful and game unlimited. 

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