center field vs centerfield

center field

noun
  • The part of a baseball field which is beyond the infield and straight ahead left if you stand on home plate and face the pitcher. 

  • The defensive position in the outfield in the middle, typically played by a player that can run fast. 

  • A central role in some activity that requires speed. 

centerfield

noun
  • The central part of the outfield 

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