pledge vs vouch

pledge

verb
  • To make a solemn promise (to do something). 

  • To deposit something as a security; to pawn. 

  • To give assurance of friendship by the act of drinking; to drink to one's health. 

noun
  • A solemn promise to do something. 

  • The personal property so pledged, to be kept until the debt is paid. 

  • A bailment of personal property to secure payment of a debt without transfer of title. 

  • A person who has taken a pledge of allegiance to a college fraternity, but is not yet formally approved. 

  • A drinking toast. 

  • An asset or person temporarily handed over to guarantee the fulfilment of something promised, under threat of permanent loss of the thing handed over; surety, security, hostage. 

  • A promise to abstain from drinking alcohol. 

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