greeting card vs playing card

greeting card

noun
  • A card, typically folded in half and available commercially, that is sent to someone as a greeting. (This entry is a translation hub.) 

playing card

noun
  • Any of the usually 52 rectangular pieces of card used to play numerous games, featuring either one to 10 pips or a picture and belonging of one of four suits. 

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