filthy vs near the knuckle

filthy

adj
  • Covered with filth; very dirty. 

  • Obscene or offensive. 

  • Very unpleasant or disagreeable. 

verb
  • To make very dirty; to saturate something with dirt. 

  • To cover in filth. 

near the knuckle

prep
  • Risqué, sexual, suggestive of impropriety. 

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