Balhae vs Xicheng

Balhae

name
  • A kingdom in southern Manchuria and northeastern Korea in the late first millennium. 

Xicheng

name
  • a subdistrict in Jingzhou, Jingzhou, Hubei, China 

  • A district in downtown Beijing, China, comprising the sections immediately west of the Forbidden City. 

  • a subdistrict in Zengdu, Suizhou, Hubei, China 

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