airmail vs mailing

airmail

noun
  • The system of conveying mail using aircraft. 

  • The items of mail so carried. 

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. 

mailing

noun
  • An act of sending mail. 

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