dismount vs unhorse

dismount

verb
  • To (cause to) get off (something). 

  • To come down; to descend. 

  • To throw (cannon) off their carriages. 

  • To make (a mounted drive) unavailable for use. 

noun
  • The part of a routine in which the gymnast detaches from an apparatus. 

unhorse

verb
  • To disrupt or unseat; to remove from a position. 

  • To forcibly remove from a horse. 

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