chew over vs revolve

chew over

verb
  • To think deeply about; to ponder or mull over. 

revolve

verb
  • To orbit a central point (especially of a celestial body). 

  • To move in order or sequence. 

  • To cause (something) to turn around a central point. 

  • To rotate around an axis. 

noun
  • The rotation of part of the scenery within a theatrical production. 

  • The rotating section itself. 

How often have the words chew over and revolve occurred in a corpus of books? (source: Google Ngram Viewer )