let something slip vs spill one's guts

let something slip

verb
  • To accidentally reveal a secret. 

spill one's guts

verb
  • To confess, or to divulge secrets, typically speaking freely and at length after a change of motive or an incentive. 

  • To vomit. 

How often have the words let something slip and spill one's guts occurred in a corpus of books? (source: Google Ngram Viewer )