irrecoverable vs unrestorable

irrecoverable

adj
  • That cannot be recovered from or made good; irremediable. 

  • Not recoverable; incapable of being recovered. 

unrestorable

adj
  • Not restorable; that cannot be restored. 

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