internecine vs invigorating

internecine

adj
  • Mutually destructive; most often applied to warfare. 

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

invigorating

adj
  • Giving strength, energy and vitality. 

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