Since the DNA matches are 4th+ cousins and I know the history of up to only my level 2 or 3 grandparents, there likely was some migration from Kerry to both Waterford and Cork of at least some of their descendants.
My Irish roots are entirely on my father's side. I have the names of dad's father (O'Brien), mother (Welch), ggrandfathers (Millerick and Bryan), ggrandmothers (FitzGibbons, Keating).
Everything earlier that is speculation and guesswork.
Somehow, my dad's parents ended up in Hartford, Connecticut from Springfield, and North Adams, Massachusetts. I've been told a lot of the Irish in the Springfield-Hartford area are from County Kerry. So, this bears out in my DNA info from Ancestry.com.
I just can't seem to figure out how.