airmail vs consign

airmail

verb
  • To send mail by air. 

  • To (unintentionally) throw the ball well over a fielder's head where that fielder is unable to make a play on the ball. 

noun
  • The items of mail so carried. 

  • The system of conveying mail using aircraft. 

consign

verb
  • To send to a final destination. 

  • To stamp or impress; to affect. 

  • To entrust to the care of another. 

  • To assign; to devote; to set apart. 

  • To transfer to the custody of, usually for sale, transport, or safekeeping. 

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