They have racing names but not called them in the kennels, they have tattoos in their ears with their numbers on which you can get all of their racing data from. So you can call them anything as they dont have a name other than if the rescue centre names them, but they wont be used to it.
Just found this out, I wasn't sure.
Taken from Google
Because registered names are often long and complex (e.g., "KL's Vanilla Ice" or "WJS LoveStory"), racing kennels, trainers, and owners use a much simpler "call name" for day-to-day handling. When greyhounds retire and are adopted, new owners frequently keep the call name or give the dog an entirely new name