countersignature vs go-ahead

countersignature

noun
  • A signature made to confirm or endorse another. 

go-ahead

noun
  • Approval, agreement, or instruction to begin or proceed. 

adj
  • Progressive; exerting leadership. 

  • Being a score which gives the scoring team or player the lead in the game. 

  • Dashing; energetic. 

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