nursery school vs playgroup

nursery school

noun
  • A school where pre-school children play and learn at the same time. 

playgroup

noun
  • A group of children who meet together for supervised play. 

  • An informal organised group providing care and activities for preschool children. 

  • A group of gamers who meet together, especially for role-playing games. 

How often have the words nursery school and playgroup occurred in a corpus of books? (source: Google Ngram Viewer )