Kiev vs Kyiv

Kiev

name

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

  • 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. 

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 Kiev and Kyiv occurred in a corpus of books? (source: Google Ngram Viewer )