Sorry I've not had time to read all the earlier posts, but yes there were Scots in Ireland before the Plantation Scots. From what I understand, in the early Middle Ages "aquatically mobile" clans like the MacDonalds (Lords of the Isles) and whoever else had a fast birlinn had interests in Ireland as well as Scotland. One clan the MacSweens / MacSweyns had their castle in Knapdale, Argyll but by the 13th Century were edged out and settled in Ireland. The story goes they later morphed as the Sweeneys. Through the Middle Ages and Renaissance, there were various instances of mutual help between Ireland and the Western Highlands possible due to their regular use of the seas. The Highland warriors who stayed to serve Irish chiefs and lords were known as Gallowglasses and were known for their iron-mail war-coats, saffron shirts and pot helmets. That's all I know off the top of my head !