attest vs confirm

attest

verb
  • To certify by signature or oath. 

  • To affirm to be correct, true, or genuine. 

  • To certify in an official capacity. 

  • To put under oath. 

  • To supply or be evidence of. 

confirm

verb
  • To administer the sacrament of confirmation on (someone). 

  • To assure the accuracy of previous statements. 

  • To strengthen; to make firm or resolute. 

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