gag vs sit on

gag

verb
  • To restrain someone's speech by blocking his or her mouth. 

  • To cause to heave with nausea. 

  • To pry or hold open by means of a gag. 

  • To choke; to retch. 

  • To experience the vomiting reflex. 

  • To restrain someone's speech without using physical means. 

  • To astonish (someone); to be at a loss for words. 

noun
  • A joke or other mischievous prank. 

  • Mycteroperca microlepis, a species of grouper. 

  • Any suppression of freedom of speech. 

  • An order or rule forbidding discussion of a case or subject. 

  • A device to restrain speech, such as a rag in the mouth secured with tape or a rubber ball threaded onto a cord or strap. 

  • a device or trick used to create a practical effect; a gimmick 

  • A convulsion of the upper digestive tract. 

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 gag and sit on occurred in a corpus of books? (source: Google Ngram Viewer )