allay vs palliate

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. 

palliate

verb
  • To placate or mollify. 

  • To cover or disguise the seriousness of (a mistake, offence etc.) by excuses and apologies. 

  • To relieve the symptoms of; to ameliorate. 

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