elutriate vs expunge

elutriate

verb
  • To decant; to purify something by straining it. 

  • To separate large and small particles through an upwardly flowing liquid or vapid stream. 

expunge

verb
  • To erase or strike out. 

  • To eliminate completely; to annihilate. 

  • To delete permanently (e-mail etc.) that was previously marked for deletion but still stored. 

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