common sense vs soft soap

common sense

noun
  • Ordinary sensible understanding; one's basic intelligence which allows for plain understanding and without which good decisions or judgments cannot be made. 

soft soap

noun
  • any fluid or semifluid soap 

  • jellyish soap made by cooking natural oils and fats with potassium hydroxide 

How often have the words common sense and soft soap occurred in a corpus of books? (source: Google Ngram Viewer )