sign on vs take up

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. 

take up

verb
  • To accept (a proposal, offer, request, etc.) from. 

  • To implement, to employ, to put into use. 

  • To review the solutions to a test or other assessment with a class. 

  • To begin doing (an activity) on a regular basis. 

  • To occupy; to consume (space or time). 

  • Synonym of take in (“tighten a belaying rope”) 

  • To resume. 

  • To pick up. 

  • To address (an issue). 

  • To shorten by hemming. 

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