Riddle me this: an Irish/British genetic genealogy question

Family history-wise, my father is half Irish and half German. All his paternal ancestors trace back to Ireland. All his maternal ancestors trace back to Germany. This is documented - I have done the legwork, and I know for a fact where all his immigrant ancestors originally hailed from, and it's either an Irish county or a German state. So explain to me, then, how my father is more than a quarter British, DNA-wise?


This is my father's genetic break-down according to AncestryDNA. As you can see, they differentiate between Irish and British. Irish is considered Irish/Scottish/Welsh, and British is considered English/Scottish/Welsh. There is the Scottish and Welsh overlap between the two, but no overlap between the Irish and English. Scandinavia I assume is from some kind of genetic influence via my father's Irish family or northern German family. But 28% British is no small chunk of change - not that we inherit DNA evenly from all our ancestors, but that's the equivalent of one full grandparent! 

I do have one theory I'm working on - my father's last name, Gorry, which we've traced back to the Kells vicinity of County Meath, Ireland, shows up a LOT in British records - England, Australia, TONS of Scottish Gorrys, and in particular, A LOT in the Isle of Man. The Isle of Man, as I've learned, is it's own sovereignty, but is considered British - it sits in the English Channel, about even with Cumbria, one of the northernmost parts of England, to the east, is just south of Dumfries and Galloway in Scotland, and is about even with County Louth in Ireland on the west. County Meath is right below County Louth, also situated on that coast. I had always thought maybe at some point some Gorrys from Ireland, some of my Gorrys, had traveled east and ended up populating the Isle of Man...but what if the migration wasn't west to east, from Ireland to Great Britain, but from east to west, and the Gorrys actually have BRITISH origins, ending up in Ireland?

I would love any input from someone who has a better grasp than I do of genetic genealogy - am I reading too much into the British/Irish differentiation? Am I making up a mystery where there is none? Or does my father's DNA support SOME kind of connection between the Gorrys of County Meath and the many, many Gorry names that pop up in English, Scottish and Isle of Man records? 

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