crux vs exterior

crux

noun
  • The basic, central, or essential point or feature. 

  • The critical or transitional moment or issue, a turning point. 

  • The hardest point of a climb. 

  • A puzzle or difficulty. 

  • A cross on a coat of arms. 

exterior

adj
  • Being from outside a country; foreign. 

  • Outdoor. 

  • Relating to the outside parts or surface of something. 

noun
  • Foreign lands. 

  • The outside part, parts or surface of something. 

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