impugn vs take to task

impugn

verb
  • To verbally assault, especially to argue against an opinion, motive, or action; to question the truth or validity of. 

take to task

verb
  • To lecture, berate, admonish, or hold somebody accountable for his or her actions. 

How often have the words impugn and take to task occurred in a corpus of books? (source: Google Ngram Viewer )