allay vs prolong

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. 

prolong

verb
  • To put off to a distant time; to postpone. 

  • To lengthen in time; to extend the duration of 

  • To become longer; lengthen. 

  • To extend in space or length. 

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