lock up vs sit on

lock up

verb
  • To stop moving; to seize. 

  • To invest in something long term. 

  • To close all doors and windows (of a place) securely. 

  • To (mistakenly) cause or have one of one's wheels to lock up (stop spinning). 

  • To lose one's forward momentum; to freeze. 

  • To imprison or incarcerate (someone). 

  • To cause (a program) to cease responding or to freeze. 

  • To stop spinning due to excessive braking torque. 

  • To travel through a flight of locks on a waterway in an uphill direction. 

  • To cease responding; to freeze. 

sit on

verb
  • To block, suppress, restrain. 

  • To take no action on; to hold in reserve without actually using. 

  • To hold an official inquiry regarding; to deliberate about. 

  • To be a member of. 

  • Used other than figuratively or idiomatically: see sit, on. 

  • To restrain (a person). 

How often have the words lock up and sit on occurred in a corpus of books? (source: Google Ngram Viewer )