vouch for vs witness

vouch for

verb
  • To affirm the truth or reliability of. 

witness

verb
  • To furnish proof of, to show. 

  • To take as evidence. 

  • To present personal religious testimony; to preach at (someone) or on behalf of. 

  • To see the execution of (a legal instrument), and subscribe it for the purpose of establishing its authenticity. 

  • To see or gain knowledge of through experience. 

noun
  • Attestation of a fact or event; testimony. 

  • One who sees or has personal knowledge of something. 

  • Someone called to give evidence in a court. 

  • One who is called upon to witness an event or action, such as a wedding or the signing of a document. 

  • Something that serves as evidence; a sign or token. 

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