I have a Rottie mix I adopted a few years ago. His name was Thom when I got him. I have a son named Tom so knew that wasn't going to work. My grandkids helped me choose his new name-Gus. He ends up with three names; Gus or Augustus or Gustav. My one grandson calls him GusGus because in our indecision I suggested we name him Gustav Augustus. He learned Gus the first day we started using it. He comes to Gustav too; knows he is in trouble. My other dog, Heidi a great dane also learned her new name fast. Her first name was Miranda and I couldn't keep that. She loves her new name. I think they associate the new name with all the love you give them.