leave vs sign on

leave

verb
  • To put; to place; to deposit; to deliver, with a sense of withdrawing oneself. 

  • To cause, to result in. 

  • To let be or do without interference. 

  • To cause or allow (something) to remain as available; to refrain from taking (something) away; to stop short of consuming or otherwise depleting (something) entirely. 

  • To transfer possession of after death. 

  • To give leave to; allow; permit; let; grant. 

  • To produce leaves or foliage. 

  • To give (something) to someone; to deliver (something) to a repository; to deposit. 

  • To depart; to go away from a certain place or state. 

  • To transfer responsibility or attention of (something) (to someone); to stop being concerned with. 

  • To depart from; to end one's connection or affiliation with. 

  • To end one's membership in (a group); to terminate one's affiliation with (an organization); to stop participating in (a project). 

noun
  • The action of the batsman not attempting to play at the ball. 

  • The arrangement of balls in play that remains after a shot is made (which determines whether the next shooter — who may be either the same player, or an opponent — has good options, or only poor ones). 

  • Permission to be absent; time away from one's work. 

  • Permission. 

sign on

verb
  • To commit oneself, as to a project, a goal, an organization, a cause. 

  • To begin broadcasting a radio or television signal, usually at the beginning of a broadcasting day and after being off the air for several hours. 

  • To join something, after signing. 

  • To apply to receive unemployment benefits. 

  • To log on; to start using a computer, radio, etc., or to start talking. 

noun
  • The time of day when a radio or television station begins broadcasting, usually after being off the air for several hours. 

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