Celtic culture existed in Ireland from the late prehistoric era until the 17th century and the Anglo-Norman Invasion. For most of its history, Gaelic Ireland was a scattered[hierarchy of territories ruled by a hierarchy of kings or chiefs, who were chosen or elected. Wars between were common. Traditionally, a powerful ruler was acknowledged as the High King of Ireland. The society was made up of clans and was structured hierarchically according to Class. Throughout this period, the economy was mainly trade. A Gaelic Irish style of dress, music, dance, sport and art were specific to the Celts.
Irish Mythology - Mythical Cycle - Book of Invasions