I made a Kilt Liner a few years ago and did a tutorial on how to make one.

I can't seem to find the tutorial. Perhaps I need to speak to the forum owner about where it went.

But basically you take a normal Cotton t-shirt.
Cut if off just under the arm holes.
Sew a length of elastic along the cut edge as a waistband.
Voila, kilt liner.

This works pretty good to keep down chafe.