Most visits to Ireland are trouble-free but you should be aware of the global risk of indiscriminate international terrorist attacks, which could be against civilian targets, including places frequented by foreigners.
Nollaig Shona Dhuit is Merry Christmas in Irish Gaelic, which is still taught in schools in Eire, the Irish Republic. Northern Ireland is part of the United Kingdom. Christmas in Ireland is a traditional holiday in both parts of the island, and very much a family and religious celebration!
Everyone has some form of tradition that is passed though generations of families, most of which we never bothering exploring.