internecine vs sinister

internecine

adj
  • Mutually destructive; most often applied to warfare. 

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

sinister

adj
  • Evil or seemingly evil; indicating lurking danger or harm. 

  • On the left side of a shield from the wearer's standpoint, and the right side to the viewer. 

  • Inauspicious, ominous, unlucky, illegitimate (as in bar sinister). 

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