Zheng Chenggong (Chinese: 鄭成功) was a military leader whose loyalty to the Ming dynasty led him to fight the new Manchu Qing (Ch’ing) dynasty until his death in 1662; because he recovered Taiwan from Dutch colonial rule, I heard a great deal about him while I was teaching English in Taiwan, and I wondered why he was known in English as Coxinga. It turns out Joel of Far Outliers has wondered too, and in the course of reading (and blogging) Coxinga and the Fall of the Ming Dynasty by Jonathan Clements he found the answer:
Coxinga … was said to have greatly impressed the bookish Emperor of Intense Warring [the remaining Ming pretender who had retreated to Fuzhou as the Manchus invaded]. Still only a youth of twenty-one, the former Confucian scholar was made assistant controller of the Imperial Clan Court. The childless Emperor also commented that he was disappointed not to have a daughter he could offer to Coxinga in marriage, and bestowed him with a new name. Once Lucky Pine [Fukumatsu], then Big Tree [Da Mu, a nickname from Sen 'Forest'], the boy was now given the appellation Chenggong, thereby making his new given name Zheng Chenggong translate literally as ‘Serious Achievement’. In a moment of supreme pride for his family, the boy was also conferred with the right to use the surname of the Ming ruling family itself. It amounted to a symbolic adoption, and he was often referred to as Guoxingye, the Imperial Namekeeper. Pronounced Koksenya in the staccato dialect of Fujian, and later transcribed by foreign observers, the title eventually transformed into the ‘Coxinga’ by which he is known to history.
Or, as the Wikipedia article linked above to his name puts it, “Koxinga or Coxinga is the Dutch Romanization of his popular name ‘Lord with the Royal Surname’ (國姓爺).”