cutting edge vs mezzotint

cutting edge

noun
  • The sharp edge of the blade of a knife or other cutting tool. 

  • The forefront, or position of greatest advancement in some field. 

mezzotint

noun
  • A form of intaglio etching in which a metal plate is roughened evenly and then smoothed to bring out an image. 

  • An etching or print made using this method. 

verb
  • To make such etchings 

How often have the words cutting edge and mezzotint occurred in a corpus of books? (source: Google Ngram Viewer )