bullpen vs roof

bullpen

noun
  • A place for someone or something to get ready. 

  • The relief pitchers of a team collectively. 

  • An enclosed area for pitchers to warm up in during a game. 

  • An enclosed area used to hold bulls. 

  • An open seating arrangement where project teams can communicate openly with minimal effort. 

roof

noun
  • The external covering at the top of a building. 

  • The top external level of a building. 

  • The upper part of a cavity. 

  • An overhanging rock wall. 

  • The surface or bed of rock immediately overlying a bed of coal or a flat vein. 

verb
  • To cover or furnish with a roof. 

  • To traverse buildings by walking or climbing across their roofs. 

  • To put into prison, to bird. 

  • To shelter as if under a roof. 

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