Translation:Mi wnes i ddweud.
The very north: Ynys Môn!
Cwrs Y Gogledd, Prifysgol Cymru, Bangor (Adran Dysgu Gydol Oes).
The verb dweud is taught as deud (an irregular verb; stem "dud-")
It's first introduced in Cwrs Wlpan (it's in the Geirfa section at the back) p370 "deud (dweud) - to say, to tell"
In my experience it's taught consistently and pretty exclusively as "deud", I remember compatriots on Uwch being unfamiliar with the spelling "dweud".
Cwrs Uwch (gorchmynion), unit 3, page 27 gives "Verb: deud, chi: dudwch/dwedwch, ti: duda/dwed".
The diversity of the language is pretty amazing isn't it!