attestation vs avowal

attestation

noun
  • A confirmation or authentication. 

  • The process, performed by accountants or auditors, of providing independent opinion on published financial and other business information of a business, public agency, or other organization. 

  • A thing that serves to bear witness, confirm, or authenticate; validation, verification, documentation. 

  • An appearance in print or otherwise recorded on a permanent medium. 

avowal

noun
  • An open declaration of affirmation or admission of knowledge. 

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