fieldwork vs fortress

fieldwork

noun
  • A temporary fortification built by troops in the field; a defensive earthwork in the field. 

  • The collection of raw data in the field, field research, field study, field studies. 

  • Work done out in the fields as opposed to that done elsewhere on the farm (e.g., barn, house, outbuildings, office). 

  • Work done out in the real world rather than in controlled conditions 

fortress

noun
  • A fortified place; a large and permanent fortification, sometimes including a town; for example a fort, a castle; a stronghold; a place of defense or security. 

  • A position that, if obtained by the weaker side, will prevent penetration by the opposing side, generally achieving a draw. 

verb
  • To furnish with a fortress or with fortresses; to guard, to fortify. 

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