square off vs undertake

square off

verb
  • To get ready for a confrontation (debate, argument, fight). 

  • To increase the boxiness of (a design). 

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 square off and undertake occurred in a corpus of books? (source: Google Ngram Viewer )