jack off vs jerk off

jack off

verb
  • To masturbate. 

  • To stimulate or please oneself in an unproductive or idle way. 

  • To manually stimulate someone sexually, generally a male. 

jerk off

verb
  • To masturbate, usually a male. 

  • To deceive. 

  • To do nothing; to waste time. 

noun
  • An act of masturbation. 

  • A stunt in which the performer is suddenly pulled off a horse, etc. by means of a cable. 

  • An annoying person. 

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