authenticate vs repudiate

authenticate

verb
  • To prove authentic; to determine as real and true. 

  • To render authentic; to give authority to, by the proof, attestation, or formalities required by law, or sufficient to entitle to credit. 

adj
  • Synonym of authentic. 

repudiate

verb
  • To reject the truth or validity of; to deny. 

  • To be repudiated. 

  • To refuse to have anything to do with; to disown. 

  • To refuse to pay or honor (a debt). 

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