I came up with for my MUD Deity character while stoned and exhausted after programming for a couple of days... that might have something to do with it. Somehow at the time I imagined that in some way it could almost be pronounced like "Silver" with the right accent... so yeah. Not my brightest moment, but the name kind of stuck

Coolest thing about the rules being so unclear in this case is that no matter what the GM chooses to do, it's "by the rules". So a GM can safely ignore all about it when it doesn't matter (urban setting) and then when it suddenly does matter (eg. wilderniss) he can make some on-the-spot rules for that specific situation without having to worry that from then on it'll have to be micromanaged in all future sessions.