Welsh tradition credited the founding of Gwynedd to the Brittonic polity of Gododdin (Old Welsh Guotodin, earlier Brittonic form Votadini) from Lothian invading the lands of the Brittonic polities of the Deceangli, Ordovices, and Gangani in the 5th century. The sons of their leader, Cunedda, were said to have possessed the land between the rivers Dee and Teifi. The true borders of the realm varied over time, but Gwynedd Proper was generally thought to comprise the cantrefs of Aberffraw, Cemais, and Cantref Rhosyr on Anglesey and Arllechwedd, Arfon, Dunoding, Dyffryn Clwyd, Llŷn, Rhos, Rhufoniog, and Tegeingl at the mountainous mainland region of Snowdonia opposite.
The name Gwynedd is believed to be an early borrowing from Irish (reflective of Irish settlement in the area in antiquity), either cognate with the Old Irish ethnic name Féni, “Irish People”, from Primitive Irish *weidh-n- “Forest People”/”Wild People” (from Proto-Indo-European *weydh- “wood, wilderness”), or (alternately) Old Irish fían “war band”, from Proto-Irish *wēnā (from Proto-Indo-European *weyH1- “chase, pursue, suppress”)– wikipedia
Looks like I may have to update my previous “demihuman and chaos activity are expanding from the center of the island” expectation.
So, to clarify: Gwynedd is the kingdom ruled by half-mad scottish hobbit sea-reavers. Think House Greyjoy. But shorter.