explain vs put lipstick on a pig

explain

verb
  • To make something plain or intelligible. 

  • To make plain, manifest, or intelligible; to clear of obscurity; to illustrate the meaning of. 

  • To give a valid excuse for past behavior. 

put lipstick on a pig

verb
  • To superficially alter something in the hope of making it seem more appealing than it is in actuality. 

How often have the words explain and put lipstick on a pig occurred in a corpus of books? (source: Google Ngram Viewer )