imperishable vs sempiternal

imperishable

adj
  • not perishable; not subject to decay; enduring permanently 

noun
  • something that does not perish, or keeps for a long time 

sempiternal

adj
  • Everlasting, eternal. 

  • Everlasting, that is, having infinite temporal duration (as opposed to eternal: outside time and thus lacking temporal duration altogether). 

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