Three Kingdoms vs Yuan

Three Kingdoms

name
  • The tripartite division of China between the states of Wei (魏 (Wèi)), Shu (蜀 (Shǔ)), and Wu (吳/吴 (Wú)), during AD 220–280, following the Han dynasty and preceding the Jin dynasty. 

  • The tripartite division of Korea between the kingdoms of Goguryeo (고구려(高句麗) (goguryeo)), Baekje (백제(百濟) (baekje)), and Silla (신라(新羅) (silla)), around 57 BC to AD 668, prior to its unification under Silla. 

Yuan

name
  • The imperial dynasty of China from 1279 to 1368. 

  • A surname from Chinese. 

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