allay vs exacerbate

allay

verb
  • To alleviate; to abate; to mitigate. 

  • To make quiet or put at rest; to pacify or appease; to quell; to calm. 

noun
  • Alleviation; abatement; check. 

exacerbate

verb
  • To make worse (a problem, bad situation, negative feeling, etc.); aggravate; exasperate. 

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