belt up vs close up

belt up

verb
  • To stop talking or chattering; to shut up. 

  • To fasten one's seat belt. 

close up

verb
  • To shut a building or a business for a period of time. 

  • To become less 'open' or communicative, to shrink back. 

  • To heal a cut or other wound 

  • To move people closer together. 

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