wallcovering vs woodchip

wallcovering

noun
  • A covering for a wall, such as wallpaper 

woodchip

noun
  • A small fibre of wood; especially such material as used to make ingrain wallpaper, aka woodchip wallpaper. See Wikipedia article on ingrain wallpaper. 

  • A small mechanically produced piece (chip) of wood, generally from 0.5 to 10 cm in diameter, used primarily as raw material for pulp, paper and construction boards, as well as fuel and mulch. 

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