Kiev vs Kievan Rus

Kiev

name
  • A former principality in Europe. The medieval principality centered on Kiev; the Kievan state or Kievan Rus. 

  • The government of Ukraine. 

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

  • A province, an oblast of Ukraine. Seat: Kyiv. 

Kievan Rus

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

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