be up to vs undergo

be up to

verb
  • To depend on, to be the choice of. 

  • To do or be involved in doing; to do (often something mischievous or inappropriate). 

undergo

verb
  • To suffer or endure; bear with. 

  • To experience; to pass through a phase. 

  • The project is undergoing great changes. 

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