The kilt is a traditional garment worn by Human males of Socttish descent. It consists of a length of tartan fabric (the tartan pattern often corresponding to the wearer's clan or regimental allegiance) with sharp pleats in the back and flat aprons on the front; the kilt is worn with various dress accoutrements including a sporran (purse) in the front, shoulder plaid attached with brooch, hose and a wide kilt belt.
Scotty was shown to wear a kilt and accoutrements as part of his dress Starfleet uniform (TOS: ""Is There in Truth No Beauty?"").