bellyscraper vs xyster

bellyscraper

noun
  • A piece of earthmoving equipment used to level land and build roads. A heavy equipment machinery with a blade on the bottom and a hopper on top, that can carry, scrape-up, and lay-down material. 

xyster

noun
  • A surgical instrument used to scrape bones. 

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