I had a pit/dane mix named Xander. He was named after Xander Cage from the movie "Triple X" because he had a tiny white spot on the back of his neck, like Xander Cage's tattoo in the movie.
Just repeat the name over and over again when you're working with him. Speak it out loud. My boy was named "Charlie" by the BO when I got him and the first thing I did was change his name to Aires. It took the BO a month or so to get it, but now the only person who slips and calls Aires "Charlie" is the BO's nine-year-old son.