When I see
Melchior I think instantly of Melkor (aka Morgoth: basically the devil in the mythology of Middle Earth).
In Quenya, Melkor means "He Who Arises In Might".
So I'm tempted to say it's unusable, but then again not everyone's as much of a geek as me and it definitely gets used anyway (mostly in Northwestern
Europe, I think)...though I have to agree
Fergus Melchior is a magical name for a cat.