need vs sit on

need

verb
  • To be obliged or required (to do something). 

  • To be required; to be necessary. 

  • To want strongly; to feel that one must have something. 

  • To have an absolute requirement for. 

noun
  • Lack of means of subsistence; poverty; indigence; destitution. 

  • A requirement for something; something needed. 

sit on

verb
  • To restrain (a person). 

  • 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. 

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

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