door prize vs game of chance

door prize

noun
  • A gift given to people who attend a meeting, party, event, etc., especially one which is given on a random basis to one or some of the attendees. 

  • A notional prize awarded to a cyclist who collides with the open door of a parked car. 

game of chance

noun
  • A game in which the outcome is at least partly determined by random variables rather than strictly by strategy. 

How often have the words door prize and game of chance occurred in a corpus of books? (source: Google Ngram Viewer )