avow vs undertake

avow

verb
  • To bind or devote by a vow. 

  • To declare openly and boldly, as something believed to be right; to own, acknowledge or confess frankly. 

  • To acknowledge and justify, as an act done. See avowry. 

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