Kievan Rus vs Russia

Kievan Rus

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

Russia

name
  • A country in Eastern Europe and North Asia, bordering on the Pacific and Arctic Oceans and the Baltic, Black, and Caspian Seas; established as an independent country in 1991 upon the dissolution of the Soviet Union, it is the largest country in the world. Co-official name: Russian Federation, formerly the Russian Soviet Federative Socialist Republic (RSFSR) (among other names) from 1917 to 1991. Capital and largest city: Moscow. 

  • The Union of Soviet Socialist Republics (a very common name, although more formally Russia, the RSFSR, was one of several constituent republics of the USSR). 

  • The Russian Empire; the tsarist empire in Russia lasting from 1721 to 1917. 

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