etch vs mezzotint

etch

verb
  • To engrave a surface. 

  • To make a lasting impression. 

  • To cut into a surface with an acid or other corrosive substance in order to make a pattern. Best known as a technique for creating printing plates, but also used for decoration on metal, and, in modern industry, to make circuit boards. 

  • To sketch; to delineate. 

mezzotint

verb
  • To make such etchings 

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. 

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