break the news vs let on

break the news

verb
  • To inform someone of something first, usually used when it will be difficult to tell the person. 

let on

verb
  • to reveal or indicate, especially unintentionally or against one's wishes 

  • Used other than figuratively or idiomatically: see let, on. 

How often have the words break the news and let on occurred in a corpus of books? (source: Google Ngram Viewer )