let out vs make known

let out

verb
  • To disclose. 

  • Of a school: to finish for the day or term, allowing the pupils to go home. 

  • To rent out. 

  • Of sound, to emit. 

  • To allow to operate at higher speed by adjusting controls. 

  • To release. 

  • To enlarge by adjusting one or more seams. 

make known

verb
  • To disclose (a secret). 

  • To announce (some information) generally. 

How often have the words let out and make known occurred in a corpus of books? (source: Google Ngram Viewer )