photogravure vs xylograph

photogravure

noun
  • A print so made. 

  • An intaglio process for printing photographic reproductions in newspapers and books. 

verb
  • To print by this process. 

xylograph

noun
  • A print taken from such an engraving. 

  • An engraving in wood or woodcut, especially one used in printing predating the Western tradition (14th c.). 

verb
  • To make a print from an engraving in wood. 

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