I think it fits in with the "loss of name / renaming" part. I interpret the loss of name near the end of the book as the reason why he has a fake / placeholder name throughout the entire book. We, as the reader, never get to know his actual name.

Am I remembering this wrong? It's been awhile since I've read the books. I thought at one point he had to give up his name, past, present, and future. Thus "Shadow" is basically a placeholder, and his real first name is forever lost.

It is a dumb name, but in all fairness, there is an explanation in-story for why his first name is so dumb. No excuse about the last name though.