An amusing diversion, and a most welcome one

I like the idea of a word based on tying up ones...
donkey?

Unfortunately, ligaculum recalls the subligar etc to my mind, which has become associated in modern usage with the loincloth and specifically the typically brief gladiatorial wear, which rather clashes the kilt itself.

Actual Roman garments resembling the kilt more closely than that are pictured, but none of them a good match - the licium sacrificial apron is too long and the decoration is wrong, the late Roman perizonium overlaps similarly, but has a distinctive knotting etc. etc.

For 'gird' I would prefer accingere which was widely used for belts etc., but obviously didn't refer to the kilt before it's time.

So what would a Roman re-enactor referring to a modern kilt call it? J.P. Wild made a very convincing case that the name used for garments made of the common checked cloth and simple tartans of the Roman period was scutulata (pl. scutulatae), from the word for squares (and also lozenges) the equivalent of calling it 'a tartan (garment)'.