become firm vs crystallize

become firm

crystallize

verb
  • to give something a definite or precise form 

  • to coat something with crystals, especially with sugar 

  • to assume a crystalline form 

  • to make something form into crystals 

  • to take a definite form 

How often have the words become firm and crystallize occurred in a corpus of books? (source: Google Ngram Viewer )