backyard vs play area

backyard

noun
  • An area nearby to a country or other jurisdiction's legal boundaries, particularly an area in which the country feels it has an interest. 

  • A person's neighborhood, or an area nearby to a person's usual residence or place of work and where the person is likely to go. 

  • A yard to the rear of a house or similar residence. 

play area

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