forget vs pencil in

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). 

pencil in

verb
  • to provisionally schedule 

  • to fill in or write in using pencil 

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