chief minister vs viceroy

chief minister

noun
  • The leader of government in many semi-autonomous and constituent federal states. 

viceroy

noun
  • One who governs a country, province, or colony as the representative of a monarch. 

  • An orange and black North American butterfly (Limenitis archippus), so named because it is similar to, but smaller than, the monarch butterfly. 

  • A zongdu. 

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