Unfortunately
Mabyn looks like one of those really badly made-up names. So I wouldn't recommend it. I also don't really know whether to say "MAH-binn" or "MAY-binn" or "MAB-inn" and the "bin" in there isn't good. I like many Welsh names (Arianwen,
Anwen) but not this one.
Mabyn EleanorMabyn RosalineMabyn Josephine
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https://www.behindthename.com/pnl/6232