blackening vs mouthful

blackening

noun
  • The act of defaming or sullying. 

  • The act or process of turning (becoming) black in colour. 

  • Any of various (dark-colored) surface treatments for metal substrates, to inhibit corrosion; on steel, generally, synonym of bluing. 

  • The result or an instance of such an act or process; a black stain or mark. 

mouthful

noun
  • A tirade of abusive language. 

  • The amount that will fit in a mouth. 

  • Something difficult to pronounce or say. 

  • Quite a bit. 

adj
  • Bombastic or awkward. 

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