A kilt was an item of clothing resembling a skirt. Many human cultures embraced this garment, including the Scottish, Irish, Romans, and Greeks.
In the year 2267, James T. Kirk, Spock, and Grang of the Wolf clan were forced to wear kilts as part of the Code Duello of Bavarya. (TOS novel: Mission to Horatius)
In 2276, a kilt was a common clothing item for Romulan servants. (TOS novel: The Romulan Way)
In 2371, the joined Trill, Keeten Planx, wore a kilt while visiting a resort on Argelius II. (NF - No Limits short story: "Through the Looking Glass")