discoid vs trencher

discoid

noun
  • A disk-shaped dental excavator designed to remove the carious dentin of a decayed tooth 

adj
  • Shaped like a disc/disk. 

trencher

noun
  • A machine for digging trenches. 

  • A plate on which food is served and/or cut. 

  • One who trenches; especially, one who cuts or digs ditches. 

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