Quote Originally Posted by JerMc
I haven't gone and looked for a 20 year old dictionary, so I could be wrong, but, I would say that this is a fairly recent addition.
From a 40+ year-old Webster's -

kilt: (kilt), n. [prob. < ON], a short, pleated skirt worn by men of the Scottish Highlands

Maybe in another few years, we will have a more accurate definition, eh? ;)