set off vs undertake

set off

verb
  • To begin; to cause; to initiate. 

  • To put into an angry mood; to start (a person) ranting or sulking, etc. 

  • To leave; to begin a journey or trip. 

  • To enhance by emphasizing differences. 

  • To offset, to compensate for: to reduce the effect of, by having a contrary effect. 

  • To deface or soil the next sheet; said of the ink on a freshly printed sheet, when another sheet comes in contact with it before it has had time to dry. 

  • To cause to explode, let off. 

undertake

verb
  • To take upon oneself; to start, to embark on (a specific task etc.). 

  • To commit oneself (to an obligation, activity etc.). 

  • To pass a slower moving vehicle on the curbside rather than on the side closest to oncoming traffic. 

noun
  • The passing of slower traffic on the curbside rather than on the side closest to oncoming traffic. 

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