box in vs keep under lock and key

box in

verb
  • To enclose by drawing a box around. 

  • To limit someone's freedom of thought, movement, expression, etc. 

  • To trap or immobilize something, usually a vehicle, by placing obstacles, usually other vehicles, around it to obstruct its free movement. 

keep under lock and key

How often have the words box in and keep under lock and key occurred in a corpus of books? (source: Google Ngram Viewer )