Si vs Xi

Si

name

  • A river in Shandong, China. 

  • A diminutive of the male given name Simon. 

  • Various prefectures of imperial China. 

  • A diminutive of the male given name Silas. 

  • A county in Anhui, China. 

Xi

name

  • A river in China, the western tributary of the Pearl. 

  • A county of Linfen, Shanxi, China. 

  • Xi Jinping, current General Secretary of the Chinese Communist Party (2012–present). 

  • A surname from Chinese 

noun

  • Capital Greek letter Ξ (X) 

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