Diolch, @siaronjames a @margarethall (or should it be ac @margarethall? 
)
These little bits and pieces that seem random but apparently aren’t always throw me. Thanks for being around to answer my questions. It’s helpful to know it doesn’t mean “me” (which I wondered, given the context), and also to see the North vs South variants.
Incidentally, the “Ac before mae” query turned into a huge, long, and very interesting discussion. You can find it here if you’re so inclined to see the tangents it went off on.