Kievan Rus vs Kyiv

Kievan Rus

name
  • A medieval principality in Eastern Europe centred around Kiev; considered an early predecessor of Russia, Ukraine and Belarus. 

Kyiv

name
  • An oblast of Ukraine. Seat: Kyiv 

  • A city, the capital, the administrative centre of Kyiv, Ukraine 

  • The Ukrainian government. 

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