This is an early image from my days making the Castles of Ireland map. However what it does illustrate quite nicely is the areas of Irish and Norman influence or the areas under control of these 2 groups in the early 1500's and prior to Irelands reconquest. The yellow pins are Norman Castles while the Green pins are Irish ones! If one clicks on this castles map (left) and steps back and squints ones eyes, one can see the areas where Norman influence predominated (in yellow), then click on the distribution of the Norman surnames in Ireland map (right) and see how the areas where Norman Surnames are found are reflected in where their Castles were built.  This Norman Surnames map shows the percentage of surnames of Norman origin in 1911 in each County. The figure never exceeds more than 33% even in Wexford which represents the hub of Norman settlement. 

Getting back to the Castles map the red pins represent Scottish Castles and I was surprised that Scottish Clans like the Bissett'ss had a long presence in Antrim. Having been brought up in Southern Ireland I had the misconceprion that all the Scots simply arrived during the plantation of Ulster that began in 1610. The plantation Bawns built to defend these new English and Scottish settlers that arrived during the plantation of Ulster are in pale blue. The purple pins are castles built by Gallowglass Clans.