employ vs sign on

employ

verb
  • To use (somebody for a job, or something for a task). 

  • To hire (somebody for work or a job). 

  • To make busy. 

noun
  • The state of being an employee; employment. 

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 employ and sign on occurred in a corpus of books? (source: Google Ngram Viewer )