deboard vs disembark

deboard

verb
  • To exit a form of transportation such as a boat, ship, airplane, trolley, streetcar or spaceship. 

disembark

verb
  • To go ashore out of a ship or boat; to leave a train or aircraft. 

  • To remove from on board a vessel; to put on shore 

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