dismount vs overfall

dismount

verb
  • To come down; to descend. 

  • To throw (cannon) off their carriages. 

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

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

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

overfall

verb
  • To fall over; to topple. 

  • To fall on or spill over so as to cover (something). 

  • To change or affect so as to pervade (something); to come over 

  • To fall over; to spill from an edge or height. 

noun
  • Part of a garment that hangs so as to cover a lower part. 

  • A turbulent section of a body of water, caused by strong currents passing over submerged ridges. 

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