impugn vs uphold

impugn

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

uphold

verb
  • To support by approval or encouragement, to confirm (something which has been questioned) 

  • To keep erect; to support; to sustain; to keep from falling 

  • To hold up; to lift on high; to elevate. 

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