befilth vs blacken

befilth

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

blacken

verb
  • To make dirty. 

  • To defame or sully. 

  • To cook (meat or fish) by coating with pepper, etc., and quickly searing in a hot pan. 

  • To become black. 

  • To cause to be or become black. 

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