Chancellor vs grand vizier

Chancellor

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

grand vizier

noun
  • A figure of great authority and power. 

  • The greatest minister of a sultan, with absolute power of attorney and, in principle, dismissable only by the sultan himself. 

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