Tiger Woods has been a pro golf and world phenomenon since the early 1990s, and he's been around so long now that it's easy to forget Tiger Woods' real name and the story behind his nickname.
Tiger Woods' real, full name is Eldrick Tont Woods. That's what's on his birth certificate. The initials ETW are what Woods has used as the name of one of his companies, ETW Corporation.
There's no clear explanation of why his parents, Earl and Kultida Woods, decided to name their son Eldrick.
The middle name, Tony, however, was likely suggested by Kultida. Loosely translated to English as "beginning," Tont is a common Thai name and a nod to Kultida's Thai heritage.
So, why the nickname Tiger? That's a nod to one of Earl Woods' buddies. Earl Woods served in the United States Army during the Vietnam War, and that's where he told people he met one of his best friends, a South Vietnamese soldier named Col. Vuong Dang Phong. Phong's nickname was Tiger, and Earl began calling his son that as an homage to him.
Earl Woods also referred to Tiger as "Sam," because he thought his son looked like a "Sam." Tiger named his daughter Sam.
Woods' nickname is just that, a nickname. Woods, as best we can tell, never changed his name formally to Tiger. Documents related to his divorce from Elin Nordegren refer to him at Eldrick Tont Woods.