erf vs schoolyard

erf

noun
  • A small inherited house-and-garden lot in a village or settlement. 

  • Stock; cattle. 

  • Inheritance; patrimony. 

schoolyard

noun
  • The grounds around a school. 

  • An open field near a school used for recreation by the students. 

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