corpus vs crux

corpus

noun
  • A body, a collection. 

  • Such a collection in form of an electronic database used for linguistic analyses. 

  • A collection of writings, often on a specific topic, of a specific genre, from a specific demographic or a particular author, etc. 

crux

noun
  • A puzzle or difficulty. 

  • 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 cross on a coat of arms. 

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