hush vs pour oil on troubled waters

hush

verb
  • To appease; to allay; to soothe. 

  • To make quiet. 

  • To become quiet. 

  • To clear off soil and other materials overlying the bedrock. 

noun
  • A mining method using water 

  • A silence, especially after some noise 

pour oil on troubled waters

verb
  • To calm, appease or quieten a person or situation. 

How often have the words hush and pour oil on troubled waters occurred in a corpus of books? (source: Google Ngram Viewer )