impair vs injure

impair

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

injure

verb
  • To damage or impair. 

  • To wound or cause physical harm to a living creature. 

  • To do injustice to. 

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