Same surprise for me. I was 18% Scandinavian, but thinking I was pretty much 100% English, Scottish, Irish, and Welsh. Seems both our ancestry had about 1/5 plundering Vikings,
The Vikings entered Ireland by longboat in the 9th century at a small coastal town called Annagassan, between Dublin to the south and Drogheda to the north. Annagassan holds a Viking Festival every once in awhile. The town's ancient name is Linn Duachaill.
Supposedly, any of the Irish names starting with "Du" or "Dub" are Viking in origin, like Dublin, a Viking settlement.