covenant vs vouch

covenant

verb
  • To make a stipulation. 

  • To enter into, or promise something by, a covenant. 

  • To enter a formal agreement. 

  • To bind oneself in contract. 

noun
  • A promise, incidental to a deed or contract, either express or implied. 

  • An incidental clause in an agreement. 

  • An agreement to do or not do a particular thing. 

  • A pact or binding agreement between two or more parties. 

vouch

verb
  • To assert, aver, or declare (something). 

  • To provide evidence or proof. 

  • To back, confirm, or support (someone or something) with credible evidence or proof. 

  • To call on (someone) to be a witness to something. 

  • To affirm or warrant the correctness or truth of (something); also, to affirm or warrant (the truth of an assertion or statement). 

  • To bear witness or testify; to guarantee or sponsor. 

  • To cite or rely on (an authority, a written work, etc.) in support of one's actions or opinions. 

  • To bear witness or testify to the nature or qualities (of someone or something). 

  • In full vouch to warrant or vouch to warranty: to summon (someone) into court to establish a warranty of title to land. 

  • Followed by over: of a vouchee (a person summoned to court to establish a warranty of title): to summon (someone) to court in their place. 

  • To express confidence in or take responsibility for (the correctness or truth of) something. 

noun
  • An assertion, a declaration; also, a formal attestation or warrant of the correctness or truth of something. 

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