Most Irish castles date from the 11th to 15th century. The Irish began to build fortifications in the form of castles soon after the Norman Invasion (1169 I think).Most of these medieval strongholds were subsequently occupied by invading lords who used them as defensive administrative headquarters. They are distinctly different to some of the royal castles or palaces found in Britain or continental Europe, in that Ireland has had no royalty for over a thousand years and so the castles served a more practical than symbolic role. The castles built in Ireland and Kerry were fortified homes for chieftains, or Anglo Norman settlers and were designed primarily for defensive purposes.
Useful Link for Castles & Forts in Kerry