Sure, horses know their names.
Otherwise, how could I call to ONE of them in the pasture by name, and ONLY get that one coming to the fence? Or call to them, and only the one I named raising his head?
You can call a horse whatever you want, but I don't change barn names for the older ones unless it stays close to their old name.
I have a horse named Mack. His previous owners all called him Mick. I didn't like that, so changed it to Mack. He knows his name and responds to it, because it's similar to the old one.
If I changed it to say, Silverado, he'd probably just look at me like I was stone cold crazy!