http://en.wikipedia.org/wiki/Kilt

"Starting with Dál Riata, the Scots and the Irish have been closely
entwined peoples.

Though the origins of the Irish kilt are disputed, it can be said with
some good deal of assurance that it originated in the Scottish
Highlands and Isles by possible Irish settlers. It could have been
developed by Scots, Irish, Norse Gaels, or possibly all together.

In contrast to the Scottish kilt, the Irish Lein-croich traditionally
was made from solid colour cloth, with black, saffron and green being
the most widely used colours. Solid colored Irish kilts can often be
seen in 19th and early 20th century photos in Ireland especially at
political and musical gatherings. The kilt was used as a symbol of
Gaelic nationalism in Ireland during this period. Tweed kilts were
also not uncommon in both Scotland and Ireland and have been popular
with sportsmen, fishermen, and hunters.

Many "Irish County" tartans were designed by Polly Wittering, first
produced in 1996 by the House of Edgar, of Perth in Scotland. Marton
Mills in West Yorkshire produced a competing "Irish County Crest...