AEW wrestler and producer Billy Gunn is reportedly unable to use the "Gunn" last name in AEW.
AEW refers to the former DX member as "Billy of The Gunn Club" and they also bill him as "Billy and Austin Gunn" when he's with his son, but officially his ring name in AEW is just Billy.
There's no word on what exactly happened with WWE lawyers. Chris Jericho previously joked on AEW commentary that Billy lost his last name in a poker game.
As seen below, the full "Billy Gunn" name was used for the graphic attached to The Gunn Club's theme song on YouTube: