resign vs sign off

resign

verb
  • To hand over (something to someone), place into the care or control of another. 

  • To quit (a job or position). 

  • To submit passively; to give up as hopeless or inevitable. 

  • To give up; to relinquish ownership of. 

sign off

verb
  • to give one's official approval to something for which it is needed 

  • To log off; to stop using a computer, radio, etc., especially to stop talking. 

  • To cease broadcasting a radio or television signal, usually at the end of a broadcasting day. 

noun
  • The closing of a radio or television station's studios and cessation of the broadcasting signal, usually overnight. 

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