postcard vs sympathy card

postcard

noun
  • A rectangular piece of thick paper or thin cardboard intended to be written on and mailed without an envelope. In the case of a picture postcard one side carries a picture or photograph. 

verb
  • To send by means of a postcard. 

  • To send a postcard to. 

sympathy card

noun
  • A greeting card sent to family members of one who has died to express regret. 

  • An attempt to score points in a discussion by portraying oneself as a victim in need of sympathy (used with the verb "play"). 

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