agree vs vouch

agree

verb
  • To yield assent to; to approve. 

  • To make a stipulation by way of settling differences or determining a price; to exchange promises; to come to terms or to a common resolve; to promise. 

  • To consent to a contract or to an element of a contract. 

  • To be in harmony about an opinion, statement, or action; to have a consistent idea between two or more people. 

  • To suit or be adapted in its effects; to do well. 

  • To give assent; to accede 

  • To correspond to (another word) in a grammatical category, such as gender, number, case, or person. 

  • To resemble; to coincide; to correspond. 

vouch

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

  • 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 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 agree and vouch occurred in a corpus of books? (source: Google Ngram Viewer )