forget vs sign up

forget

verb
  • To lose remembrance of. 

  • To unintentionally not do, neglect. 

  • To unintentionally leave something behind. 

  • To cease remembering. 

  • Euphemism for fuck, screw (a mild oath). 

sign up

verb
  • To add one's own name to the list of people who are participating in something (including amateur, but not professional, teams) 

  • To agree to purchase some good or service. 

  • To add a name to the list of people who are participating in something. 

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