induct vs sign on

induct

verb
  • To bring in as a member; to make a part of. 

  • To draft into military service. 

  • To formally or ceremoniously install in an office, position, etc. 

  • To introduce into (particularly if certain knowledge or experience is required, such as ritual adulthood or cults). 

sign on

verb
  • To join something, after signing. 

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

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