My wife used to work at a Japanese company, where all the employees chose an official American first name for the convenience of the non-Asian employees. I don't know if they changed them legally, but it's what they were called around the office. They called my wife "Mary-san"
In college I knew a Vietnamese immigrant whose given name was Hong Ngoc, which means Rose Jade IIRC, but she'd been christened Theresa on moving to the US.
On the other hand, I once knew a Caucasian US native who had a Vietnamese given name because her mother taught English as a second language to Vietnamese immigrants. So people's names don't always match their ethnicities.
