dak vs recorded delivery

dak

noun
  • A post system by means of transport relays of horses stationed at intervals along a route or network, carrying mail and passengers. 

  • A dak bungalow. 

verb
  • To suddenly pull down someone's pants as a prank; to pants. 

recorded delivery

noun
  • A form of postal delivery where the sender receives a receipt of postage, and the receiver must sign upon receiving it 

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