first minister vs viceroy

first minister

noun
  • The principal minister of a ruler or state. 

  • A leader of a devolved government such as Scotland, Wales, or Northern Ireland. 

  • The prime minister or a provincial or territorial premier. 

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 first minister and viceroy occurred in a corpus of books? (source: Google Ngram Viewer )