bastion vs king post

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. 

king post

noun
  • A central vertical supporting post used in architecture and bridge as well as in aircraft and ship design. 

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