At least, that's my best attempt at "Happy St. Patrick's Day" in Icelandic. In honor Patrick Snakesbane, you've managed to navigate to a rather Germanically-focused blog. To get you back on track, here's something vaguely relevant:
The Viking Age in Ireland
Scandinavian settlements were pretty far-flung in the middle ages: North America ("Vinland"), Greenland, Iceland, Ireland (Dublin/Dyflin), Scotland, the Hebrides, Shetland, and Orkney islands, England (the Danelaw, York/Jorvik, etc.), Normandy, the Baltics, even into Russia and beyond.
Only in Iceland--"a retirement home for aging Vikings", as one modern editor of the sagas put it--did the language of Old Norse survive, and relatively unchanged at that. Everywhere else, linguistic indications of their presence are much more subtle: Mix Norse and Old French and you have the Old Norman dialect, which then was brought to England, mixed with the already Norse-influenced Old English, and Anglo-Norman is born, only to give way to Middle English by Chaucer's day.
Celtic and Germanic tribes have a long history of interaction--peaceful or otherwise. Celts already occupied much European land when Germanic tribes first moved down into Bavaria, west into Gaul, and over the sea into the British Isles. The Gauls saw rule by Romans and Franks, Celts in northern Italy dealt with Lombards and Goths, and the British Isles for the last 1600 years have been to varying degrees in varying areas a jumble of Pict, Irish, Scot, Welsh, Norwegian, Dane, Saxon, Norman, so that the very word "British", originally referring to Celts such as the Welsh, can refer to Celt or Germanic, depending on context and the time period you're talking about.
Happy St. Patrick's Day, and make sure you have a ride home tonight. ;-)