approval vs go-ahead

approval

noun
  • An expression granting permission; an indication of agreement with a proposal; an acknowledgement that a person, thing, or event meets requirements. 

  • Something mailed by a seller to a collector to match their stated interests; the collector can approve of or return the item. 

  • An expression of favorable acceptance and encouragement; a compliment that also condones. 

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 approval and go-ahead occurred in a corpus of books? (source: Google Ngram Viewer )