internecine vs murderous

internecine

adj
  • Mutually destructive; most often applied to warfare. 

  • Characterized by struggle within a group, usually applied to an ethnic or familial relationship. 

murderous

adj
  • Of, characterized by, or pertaining to murder or murderers. 

  • Very difficult. 

  • Of an object: used to commit murder; capable of causing death; deadly, fatal. 

  • Of a person: intending or likely to commit murder; bloodthirsty, homicidal. 

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