assuage vs smooth down

assuage

verb
  • To lessen the intensity of, to mitigate or relieve (hunger, emotion, pain etc.). 

  • To pacify or soothe (someone). 

smooth down

verb
  • To render smooth, to remove roughness from 

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