impair vs uglify

impair

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

uglify

verb
  • To make ugly; to destroy or worsen the appearance or attractiveness of. 

  • Synonym of minify 

  • To become ugly. 

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