Chancellor vs crux

Chancellor

noun
  • An honorific for the head of state of a republic in Germany. 

crux

noun
  • A cross on a coat of arms. 

  • 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. 

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