At the risk of putting the cat amongst the pigeons, I have to raise the Irish question.

And no, let me first say I don't mean why do tartan kilt wearers get asked if they are Irish? That one is easily answered, at least in regard to the US. Most pipe bands in the US represent police or fire departments, who in turn used to be (and often still are) staffed mainly by Irish Americans, and pipe bands are most Americans experience of people wearing kilts.

What I mean is that some of us wear kilts to represent the Emerald Isle, which was not one of the options in the original question.

The Gaels came to Scotland from Ireland (although there have been some here who even dispute that) and developped the kilt over a period of time, in Scotland, from the Irish brat (cloak, rhymes with bratwurst). Then, in the celtic revival of the 19th century, the Irish kilt appeared, usually solid green or solid saffron to distinguish it as Irish and not Scottish (there are explicable reasons for both of those colours, but how much time do you have?). This makes limited sense, as there were both tartan brats (otherwise why would Scottish kilts be tartan?) and also solid coloured Scottish kilts, but it does answer the question of how to stop the man in the street (or the man on the Clapham omnibus) from thinking it was Scottish. The Irish tartan kilt is a more recent development, and doubtless suffers from the problem that most people take it for Scottish, but that horse is out of the stable and has bolted.