tell tales out of school vs tip off

tell tales out of school

verb
  • To reveal confidential or sensitive information; to gossip. 

tip off

verb
  • To alert or inform (someone), especially confidentially. 

  • To begin. 

  • To use a particular brush technique for producing a flawless surface on a wet coat of paint. 

  • To put the ball in play by throwing it up between two opponents. 

How often have the words tell tales out of school and tip off occurred in a corpus of books? (source: Google Ngram Viewer )