missive vs special delivery

missive

noun
  • Letters sent between two parties in which one makes an offer and the other accepts it. 

  • A written message; a letter, note or memo. 

adj
  • Specially sent; intended or prepared to be sent. 

special delivery

noun
  • A particular posted letter or package which is delivered in this manner; a particular act of conveying such letters or packages to one or more recipients. 

  • A kind of postal service in which, for an extra fee, letters and packages are delivered in a highly expedited manner by a special courier. 

  • Something—whether desirable or undesirable—which is intentionally given to a specific individual or which an individual receives rapidly and unexpectedly; the personalized, direct quality of the transmission of such an item. 

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