countersignature vs validation

countersignature

noun
  • A signature made to confirm or endorse another. 

validation

noun
  • Something, such as a certificate, that validates something; attestation, authentication, confirmation, proof or verification. 

  • The process of identifying a new prisoner's gang affiliation. 

  • The process whereby others confirm the validity of one's emotions. 

  • The act of validating something. 

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