Kilt with a sheet of linen on the inside
Many years ago, while living in Canada, I was attending a function that required I wear a kilt. I did not own one, but we had neighbors who were an older couple from East Lothian.
The ol' dear marched over one morning with a bottle of whiskey in one hand and a suit bag in the other. We ended up making haggis, drinking whiskey, and learning about kilts.
Long story short, she loaned me her husband's "proper" kilt (which weighed about a ton) and all the accessories. The first thing I noticed was the soft piece of linen attached to the front on the inside ... this clootie was soft and detachable, and placed in just the right place to protect a man'spride. When I asked, she replied: for wearing it regimental, ye Ken?
According to her, it was the only True way of telling a men's kilt. Wash the linen and not the kilt.
That day began my love of highland whiskey and the appreciation of the kilt!
BTW: I married a lass from Scotland almost 40 years ago.