sempiternally vs unperishably

sempiternally

adv
  • In a sempiternal manner; eternally. 

  • in an everlasting manner, as to have an infinite temporal duration; as opposed to eternally or timelessly, as to exist outside time 

unperishably

adv
  • In an unperishable manner. 

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