Gaelic Ireland (Irish: Eire Ghaidhealach) was the Gaelic political and social order, and associated culture, that existed in Ireland from the prehistoric era until the early 17th century. Before the Norman invasion of 1169, Gaelic Ireland comprised the whole island. Thereafter, it comprised that part of the country not under foreign dominion at a given time. For most of its history, Gaelic Ireland was a "patchwork" hierarchy of territories ruled by a hierarchy of kings or chiefs, who were elected through tanistry.

Throughout the Middle Ages, the common clothing amongst the Gaelic Irish consisted of a brat (a woollen semi circular cloak) worn over a leine (a loose-fitting, long-sleeved tunic made of linen). For men the leine reached to their ankles but was hitched up by means of a crios (pronounced 'kriss') which was a type of woven belt. The leine was hitched up to knee level. (Gaelicattire.com) Women wore the leine at full length. Men sometimes wore tight-fitting trews (Gaelic triubhas) but otherwise went bare-legged. The brat was simply thrown over both shoulders or sometimes over only one. Occasionally the brat was fastened with a dealg (brooch), with men usually wearing the dealg at their shoulders and women at their chests. The ionar (a short, tight-fitting jacket) became popular later on. In Topographia Hibernica, written during the 1180s, Gerald de Barri wrote that the Irish commonly wore hoods at that time (perhaps forming part of the brat), while Edmund Spenser wrote in the 1580s that the brat was (in general) their main item of clothing. Gaelic clothing does not appear to have been influenced by outside styles.  Women invariably grew their hair long and, as in other European cultures, this custom was also common among the men. It is said that the Gaelic Irish took great pride in their long hair--for example, a person could be forced to pay the heavy fine of two cows for shaving a man's head against his will. For women, very long hair was seen as a mark of beauty. Sometimes, wealthy men and women would braid their hair and fasten hollow golden balls to the braids. Another style that was popular among some medieval Gaelic men was the glib (short all over except for a long, thick lock of hair towards the front of the head). A band or ribbon around the forehead was the typical way of holding one's hair in place. For the wealthy, this band was often a thin and flexible band of burnished gold, silver or findruine. When the Anglo-Normans and the English colonized Ireland, hair length came to signify one's allegiance. Irishmen who cut their hair short were deemed to be forsaking their Irish heritage. Likewise, English colonists who grew their hair long at the back were deemed to be giving in to the Irish life.  Gaelic men typically wore a beard and mustache, and it was often seen as dishonourable for a Gaelic man to have no facial hair. Beard styles varied - the long forked beard and the rectangular Mesopotamian-style beard were fashionable at times.

What is a leine?
the common clothing amongst the Gaelic Irish