autograph vs countersign

autograph

noun
  • A person's signature used as a mark of formal approval. 

  • A person’s own handwriting, especially the signature of a famous or admired person. 

  • A manuscript in the author’s handwriting. 

verb
  • To write something in one's own handwriting 

  • To sign, or write one’s name or signature on a book etc 

adj
  • Made by the artist himself or herself; authentic. 

  • Written in the author’s own handwriting. 

countersign

noun
  • A second signature added to a document to affirm the validity of the signature of the first person. 

  • The response to a sign or signal. 

verb
  • To sign on the opposite side of (a document). 

  • To add a second signature to a document, affirming the validity of the signature of another person. 

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