bastion vs bulwark

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. 

bulwark

noun
  • A defensive wall or rampart. 

  • A defense or safeguard. 

  • A breakwater. 

  • Any means of defence or security. 

  • The planking or plating along the sides of a nautical vessel above her gunwale that reduces the likelihood of seas washing over the gunwales and people being washed overboard. 

verb
  • To fortify something with a wall or rampart. 

  • To provide protection of defense for something. 

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