We have "soda bread" in Ireland that is very similar to the recipe mekidsmom gave ( see http://en.wikipedia.org/wiki/Soda_bread ). The main difference is that we don't add butter. it's usually shaped into farls ( it starts off circular and is cut into quarters.) and is cooked on a flat griddle. There are pictures of a farl on the link. Because it is cooked on the griddle, it is flipped over to cook, which keeps the farl from rising very high.
The buttermilk is a souring agent that reacts with the baking soda to make the bread rise. I'd wondered if the Scotch-Irish links with the carolinas, tennesee and kentucky might have been a reason for the similarity, but the link suggests that soda only came in in the 1840's.
My father would talk about having buttermilk for breakfast every morning when he lived in fermanagh during the war. Interestingly, the "fiery" preacher, Rev Ian Paisley used to call alcohol " the devil's buttermilk" !
I don't see it so much in the ROI, lena - soda bread that is - there's plenty of the devil's buttermilk ?