intelligibility vs soft soap

intelligibility

noun
  • The quality of recorded speech of every word being understandable. 

  • That which is intelligible; the degree to which something is intelligible. 

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 intelligibility and soft soap occurred in a corpus of books? (source: Google Ngram Viewer )