impugnation vs reproof

impugnation

noun
  • The act of appealing or revoking 

  • The act of impugning 

reproof

noun
  • An act or instance of reproving or of reprobating; a rebuke, a reproach, an admonition. 

verb
  • To proof again. 

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