bastion vs field work

bastion

noun
  • A projecting part of a rampart or other fortification. 

  • A well-fortified position; a stronghold or citadel. 

  • A person, group, or thing, that strongly defends some principle. 

  • Any large prominence; something that resembles a bastion in size and form. 

verb
  • To furnish with a bastion. 

field work

noun
  • A temporary fortification in the field 

  • The collection of raw data, in the field 

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