allay vs quieten

allay

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

  • To alleviate; to abate; to mitigate. 

noun
  • Alleviation; abatement; check. 

quieten

verb
  • To become quiet. 

  • To make quiet. 

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