attestation vs oath

attestation

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

  • 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 confirmation or authentication. 

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

oath

noun
  • A solemn pledge or promise that invokes a deity, a ruler, or another entity (not necessarily present) to attest the truth of a statement or sincerity of one's desire to fulfill a contract or promise. 

  • A light, irreverent or insulting appeal to a deity or other entity. 

  • A curse, a curse word. 

  • A statement or promise which is strengthened (affirmed) by such a pledge. 

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