playfield vs playing field

playfield

noun
  • A playing field. 

  • The area within which a game (especially a video game) is played. 

playing field

noun
  • A field on which a game, especially a ball game, is played. 

  • Any place or context within which competitive activity takes place, such as market competition between companies. 

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