emperor vs vizier

emperor

noun
  • The male monarch or ruler of an empire. 

  • A large, relatively valuable marble in children's games. 

  • Any of various butterflies of the subfamily Charaxinae. 

  • Specifically, the ruler of the Holy Roman Empire; the world-monarch. 

  • Any of various large dragonflies of the cosmopolitan genus Anax. 

  • An emperor penguin. 

  • The fourth trump or major arcana card of the tarot deck. 

  • Any monarch ruling an empire, irrespective of gender, with "empress" contrasting to mean the consort of an emperor. 

  • Any fish of the family Lethrinidae. 

vizier

noun
  • vicegerent, viceroy 

  • A fairy chess piece that can only be moved one space up, down, left or right. 

  • An ancient Mesopotamian 𒈛 (sukkal). 

  • The highest-ranking official or minister in ancient Egypt or Ebla; a chief administrator or a chancellor. 

  • A high-ranking official or minister in an Islamic government, especially in the Ottoman Empire. 

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