internecine vs pestilential

internecine

adj
  • Mutually destructive; most often applied to warfare. 

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

pestilential

adj
  • Having a harmful moral effect (especially one that is believed to spread in the manner of pestilence). 

  • Caused by pestilence. 

  • Causing irritation or annoyance. 

  • Spreading in the manner of pestilence. 

  • During which pestilence spreads. 

  • Producing, spreading, promoting or infected with pestilence; causing infection. 

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