batten down vs loosen

batten down

verb
  • To close or make watertight, referring to hatches and cargo. 

  • To secure. 

  • To prepare for adversity. 

loosen

verb
  • To make loose. 

  • To free from restraint; to set at liberty. 

  • To become unfastened or undone. 

  • To relieve (the bowels) from constipation; to promote defecation. 

  • To become loose. 

  • To disengage (a device that restrains). 

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