bank up vs bulwark

bank up

verb
  • To make a mound to guard against something. 

  • To press a mound of something against something else. 

bulwark

verb
  • To provide protection of defense for something. 

  • To fortify something with a wall or rampart. 

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. 

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