Den - there are two periods that I can think of involving the Irish in slavery. In the Celtic Period, slavery was a way of life, along with cattle stealing. But I don't think that the Irish were any worse than anybody else in those times - not much respect for life or property anywhere in the World.

During the Commonwealth Period gangs roamed the country adding more poor Irish slaves to the 'prisoners of war' who were shipped to the West Indies.

There were of course Irish involved in the Transatlantic Slave Trade, the same as English, Welsh and Scottish, but they don't deserve any particular notoriety for this. The major blame should go to the Bristol and Liverpool 'merchants' and the owners of estates in the New World.

So on the whole I believe that the Irish were more predated upon by the British, Vikings and Arabs than they can be accused of being 'notorious slavers'. But there was a period (Romano-British) when it was considered risky to sail the Irish Sea for the fear of Irish pirates/slavers. Of course there are few written sources from this period and no real independent views. But it did provide Ireland with a Patron Saint!