approximate vs belly up to

approximate

verb
  • To come near to; to approach. 

  • To carry or advance near; to cause to approach. 

  • To estimate. 

adj
  • Nearing correctness; nearly exact; not perfectly accurate. 

  • Approaching; proximate; nearly resembling. 

belly up to

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