This was a gift for a Great Dane owner. The idea behind this was to use a gray shirt and apply a black print to complement the dog (Atos), since he is a gray and black Dane which is a considered a breeding mistake and are usually put down soon after birth. The owner saved this one from that fate and has great affection for him.
The text is something that his owner likes to say when Atos isn't being obedient, an internal joke. Thats what makes the gift so personal, as they should be.