rotogravure vs wood engraving

rotogravure

noun
  • A printing process by which the paper is rolled through intaglio cylinders. 

  • A print made by such a method. 

  • A portion of a printed work produced by this method. 

wood engraving

noun
  • A print taken from such an engraving. 

  • A variation of the woodcut method executed with a different tool (burin) and different wood (end grain), allowing for more detailed images. 

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