attorn vs undertake

attorn

verb
  • To transfer one's obligations from a person to another person. 

  • To consent to the transfer of one's obligations as tenant under a lease to a new landlord. 

  • To acknowledge the jurisdiction of (a particular court) over one's dispute. 

undertake

verb
  • 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. 

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

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

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