coupon vs passkey

coupon

noun
  • A section of a ticket, showing the holder to be entitled to some specified accommodation or service, as to a passage over a designated line of travel, a particular seat in a theater, a discount, etc. 

  • A small sample of a bulk material, prepared so that test failure will be representative. 

  • Any interest payment made or due on a bond, debenture or similar (no longer by a physical coupon). 

  • The letter sent to parliamentary candidates at the 1918 general election, endorsing them as official representatives of the coalition government. 

  • A person's face. 

  • A voucher issued by a manufacturer or retailer which offers a discount on a particular product. 

verb
  • To use coupons to a such extent that makes the user actively looking for coupons in magazines, online and whatever they can be found. 

passkey

noun
  • A key, especially in a hotel, that allows someone in authority to open any door. 

  • A key for entering a house or other building. 

  • A password. 

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