heal vs impair

heal

verb
  • To make better from a disease, wound, etc.; to revive or cure. 

  • To become better or healthy again. 

  • To reconcile, as a breach or difference; to make whole; to free from guilt. 

noun
  • A spell or ability that restores hit points or removes a status ailment. 

impair

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

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