. . .
Mel can stand on its own. According to my Irish cousin,
Mel was an ancient Irish (male) saint. She named one of her sons
Mel, not short for anything. So that's an option if you'd like.
Personally, I love the sound of it because it means "honey" in Russian (and Greek too, I think.) I especially love it as a nn for
Melanie and
Imelda.