Celestial為什麼會有中國人的意思？是源於天朝還是另有原因？

是的。

Celestial was a term referring to Chinese emigrants to the United States, Canada, and Australia during the 19th century.

The term was widely used in the popular mass media of the day.The term is from Celestial Empire (Tianxia, Chinese: 天朝; pinyin: Tiāncháo) a traditional name for China.

來自http://en.wikipedia.org/wiki/Celestial_(Chinese)

來自維基，大意如下：

Celestial本意「天的，天空的」，在19世紀曾廣泛用來指移民到美國、加拿大、澳大利亞的中國人。這個用法的來源是Celestial Empire（天朝，中國的舊稱）。