approve vs impair

approve

verb
  • To officially sanction; to ratify; to confirm; to set as satisfactory. 

  • To make profit of; to convert to one's own profit — said especially of waste or common land appropriated by the lord of the manor. 

  • To consider worthy (to); to be pleased (with); to accept. 

  • To regard as good; to commend; to be pleased with; to think well of. 

impair

verb
  • To weaken; to affect negatively; to have a diminishing effect on. 

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