send word vs tip off

send word

verb
  • To notify via a delivered message. 

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 send word and tip off occurred in a corpus of books? (source: Google Ngram Viewer )