The mouse knows its name. It is the only thing that the mouse can remember from his life before he came here. That is how the 'Hideout' takes most characters.
[I should know - I am the Hideout]
But he can't make the human understand. "Mathew," he tries to say. All that comes out is a squeak.
That is odd. The mouse is sure that he used to be able to speak properly. Has he always been a mouse?
A good question. He will have to think about that one.