[gdhbcc]

I'm pretty sure the author made a mistake in the first line.

Meiga does not mean "witch or wise woman", it refers to a "soft" or "sweet" woman.

Perhaps there was confusion with that word and "maga", which does mean "witch" or "wise woman"? They sound very similar when spoken

[thr085446655]

It does mean witch in galician (probably in portuguese as well). Kind of a soft witch, and not an evil one. Galicia had, until recently, quite colorful magical traditions.

Your etymology seems plausible.

[jorgemendes]

"Meiga" does not mean "Witch" in Portuguese, it means a "gentle woman".