formation vs trenches

formation

noun
  • An arrangement of moving troops, ships, or aircraft, such as a wedge, line abreast, or echelon. Often "in formation". 

  • An arrangement of players designed to facilitate certain plays. 

  • A structure made of two categories, two functors from the first to the second category, and a transformation from one of the functors to the other. 

  • The act of assembling a group or structure. 

  • The process during which something comes into being and gains its characteristics. 

  • Something possessing structure or form. 

  • A layer of rock of common origin. 

  • A grouping of military units or smaller formations under a command, such as a brigade, division, wing, etc. 

  • The process of influencing or guiding a person to a deeper understanding of a particular vocation. 

trenches

noun
  • The front line of any field of endeavor, as the line of scrimmage in American football, patrol duty for a policeman. 

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