get the ball rolling vs undertake

get the ball rolling

verb
  • To begin; to start some action; to set in motion. 

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 get the ball rolling and undertake occurred in a corpus of books? (source: Google Ngram Viewer )