jettison vs retain

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. 

retain

verb
  • To hold back (a pupil) instead of allowing them to advance to the next class or year. 

  • To employ by paying a retainer. 

  • To keep in one's pay or service. 

  • To keep in possession or use. 

  • To hold secure. 

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