ascertain vs repudiate

ascertain

verb
  • To find out definitely; to discover or establish. 

repudiate

verb
  • To be repudiated. 

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

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

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

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