irrecoverable vs unrecoverable

irrecoverable

adj
  • Not recoverable; incapable of being recovered. 

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

unrecoverable

adj
  • Not recoverable; that cannot be recovered. 

  • From which recovery is not possible. 

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