befilth vs slotter

befilth

verb
  • To cover with filth; make filthy; begrime. 

slotter

verb
  • To make filthy; to foul. 

noun
  • Filth. 

  • A tool used to make a mortise, or to shape the sides of an aperture. 

  • Such a tool that is much like a shaper but with a smaller ram, vertically mounted. 

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