The kilt was banned in 1746, forcing the Scots to wear “the unmanly dress of the Lowlander.”
In the 18th century CE the British monarchy were not exactly fans of the Scottish clans. The (Catholic) King of England, Ireland, and Scotland had been deposed in 1688 in favour of his (Protestant) daughter, and for the next half a century a series of rebellions and uprisings attempted to restore the throne to the old king’s Catholic successors.
In 1745, many of the Scottish clans invaded England as part of the last such uprising. It was not successful, and the parliamentary punishment for the invasion was the Act of Proscription 1746. It attempted to disarm the highlands, break the feudal control held by the Scottish lords, and – shockingly – it banned the kilt.
Specifically, the Dress Act 1746 forbade
the Plaid, Philabeg, or little Kilt, Trowse, Shoulder-belts, or any part whatever of what peculiarly belongs to the Highland Garb; and that no tartan or party-coloured plaid of stuff shall be used for Great Coats or upper coats
(A quick word of explanation: the original kilt, known as the Great Kilt, covered the whole body like a cloak. The little kilt is the kind we know today. The Dress Act banned them both.)
A special exception was made for the army, but otherwise this act killed off the kilt for the next thirty-six years. The ban was finally lifted in 1782, with this extremely melodramatic announcement:
Listen Men. This is bringing before all the Sons of the Gael, the King and Parliament of Britain have forever abolished the act against the Highland Dress; which came down to the Clans from the beginning of the world to the year 1746. This must bring great joy to every Highland Heart. You are no longer bound down to the unmanly dress of the Lowlander.
As my wife observed, the kilt dates back to the beginning of the world? Interesting boast. The popularity of the modern kilt only truly returned when King George IV visited Scotland in 1822 – it was the first time a British monarch had stepped foot in Scotland in about two hundred years, and he wore a kilt when he did so. Also pink tights.