sempiternity vs spiritual world

sempiternity

noun
  • Eternity; a seemingly everlasting period of time. 

  • Existence within time but infinitely into the future, as opposed to eternity, understood as existence outside time. 

spiritual world

noun
  • The afterlife. 

  • A metaphysical plane of existence parallel to the material world and occupied by spirits and other unearthly forces. 

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