hang up one's boots vs jettison

hang up one's boots

verb
  • retire, call it a day 

jettison

verb
  • To let go or get rid of as being useless or defective. 

  • To eject from a boat, submarine, aircraft, spaceship or hot-air balloon, so as to lighten the load. 

noun
  • Items that have been or are about to be ejected from a boat or balloon. 

  • The action of jettisoning items. 

How often have the words hang up one's boots and jettison occurred in a corpus of books? (source: Google Ngram Viewer )