let go vs sit on

let go

verb
  • Used other than figuratively or idiomatically: see let, go. 

  • To dismiss from employment. 

  • To release from one's grasp; to go from a state of holding on to a state of no longer holding on. 

  • To ignore (a comment, etc.). 

  • To emotionally disengage or to distract oneself from a situation. 

  • To fail to maintain a standard of appearance, behavior, or performance. 

  • To gain weight 

sit on

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

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

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

  • To block, suppress, restrain. 

  • To be a member of. 

  • To restrain (a person). 

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