It not like that - Northern Ireland is considered a different country to it's Southern part. For many years, Northern Ireland had what are referred to as "troubles" because of clashes between the Catholic and Protestants. Rifts existed in families for many generations and religious hatred. Belfast was in the thick of the troubles and I understand that even some streets were split with one side being one religion and the other side being opposing religion. Much violence and many, many shootings. I even hear that children escorted down street to school by gunmen.
But I think although some undercurrents (?) of that mindset, much of troubles now settled. And it not like that throughout and Southern Island totally different.
It was in Northern Ireland in the thick of the troubles that the terrorist group called the IRA (Irish Republic Army, I think) were based. This group responsible for many bombs. One in London Harrods maybe, one Christmas time.
I think 33 Daisies saying to avoid wearing cross because of religious war background but I think this no accurate reflection of today and it not like you would be going into the poverty areas is it? Or the housing estates where violence is more likely. Every country have areas that best avoided as tourist but avoiding wearing a cross rather over reactionary.
Sweet Milk and Tobacco likely something to do with the Leprechauns. I not heard that particular reference before. Leprechauns are like Irish Folklore fairy who causes mischief.