I don't know. However just be aware that the modern 'skirt-like' Scottish kilt really only dates from the eighteenth century. What was essentially the same as the modern kilt was known as the small kilt or walking kilt and this was probably invented by Thomas Rawlinson, an English Quaker from Lancashire in the 1720s. This was when water-powered Lancashire weaving mills were starting to greatly increase the amount of woolen cloth available and also when, following the 1707 Act of Union between England and Scotland, and with military action being taken against the rebellious Scottish Jacobites, the remote highlands of Scotland were starting to come under more control and be more accessible to outsiders. Thomas Rawlinson likely just saw these developments as giving him an opportunity to sell more cloth in Scotland. Prior to that the usual costume in the Scottish highlands was the belted plaid or great kilt (feileadh mòr) which was a full-length garment made of a large rectangle of cloth (made from two loom-widths sewn together, so about 60 inches wide, and up to 7 yards in length), whose upper half could be worn as a cloak draped over the shoulder or brought up over the head as a hood, with only the lower part belted around the waist to form a skirt around the legs.

The full great kilt or plaid was only usually worn by the highland clans and even then the earliest references to it are only from the sixteenth century. My Scottish ancestors were lowland Scots from Lothian and Fife, and the men most likely wore exactly the same as the majority of western Europeans, that is in medieval and renaissance times a pair of tight-fitting hose (tights/leggings) held up with points (laces) attached to a doublet (a close-fitting under jacket), then later on they would have worn breeches with stockings, and finally trousers or perhaps trews, which were a uniquely Scottish style of close-fitting trouser. As clothing in the impoverished, rainy and boggy highlands, the full plaid was probably very practical as it left the lower legs bare and so didn't get sodden with water and mud, while the upper part functioned as a cloak and hood against the weather. The whole garment could also readily double as a combined sleeping blanket and groundsheet when out on the moors tending to the huge herds of cattle that were the mainstay of the highland economy.

There is a fondly held belief among some in the British military that during the First World War the Germans referred to the Highland regiments as ‘devils in skirts’ or ‘ladies from hell’. There is, however, little or no evidence for this. Indeed, the fashion for women in the decades leading up to and during the First World War was not for skirts at all but for full-length dresses. This would put a further question mark over the origin of those nicknames. 

Very few women or girls before the First World War would have worn kilts. That said - this picture from the 19th Century shows a lady in a plaid dress with her 2 daughters in tartan skirts and her son in a kilt.  



(The Duchess of Strathearn with her children, 1890s)

After the First World War as the length of women’s skirts shortened there were some examples of women and girls wearing tartan skirts in the 1920s although it was still very rare. By the 1930s it had become slightly more prevalent, notably with the British royal children Elizabeth and Margaret being photographed in tartan skirts during that decade. 

In the 1940s Ginger Rogers wore a kilt during the number My One and Only Highland Fling alongside the equally kilted Fred Astaire in the 1949 musical The Barkleys of Broadway. 2 years later in 1951, the British royals were again in the limelight, when Queen Elizabeth and her daughters Elizabeth and Margaret (this time as adults) all wore kilts while out for a walk in Balmoral on the occasion of Margaret’s 21st birthday. During the rest of the 1950s the wearing of plaid skirts became increasingly popular among women, particularly in North America. By the end of that decade and into the early 1960s plaid skirts were already being incorporated as uniform in many schools. With the advent of the miniskirt in the 1960s, tartan miniskirts became popular. 1968 would see, among others, the likes of Brigitte Bardot and Scotland’s very own Lulu sporting plaid minis. 
  
In 1972, when Gordonstoun School in Morayshire became one of the first private schools in Britain to go co-educational, the uniform for the new intake of girls was a tartan skirt. The school’s public image was very high-profile at the time as it was where the then Prince Charles had been educated and where his younger brothers would also attend. Charles, however, is said to have disliked his time there referring to it as ‘Colditz with kilts’. Since then, the plaid skirt has become popular as school uniform for girls around the world ranging from North America to Africa to East Asia. As far as I’m aware I don’t think that Scotsmen are that bothered about cultural appropriation because, as Meles has pointed out regarding the 18th Century historical invention, there is also a big difference between a plaid skirt and a tartan kilt.

In the 17th and early 18th centuries, when many male highlanders still routinely wore the great plaid, their womenfolk wore something similar, called the earasaid or arisaid. This again was a large rectangular piece of cloth that could be pleated and fixed around the waist with a belt, with the spare material wrapped around the shoulders, fixed with a pin or broach at the front or on one shoulder and with enough surplus material to form a hood that could be pulled up in bad weather. The arisaid was not in itself used as a dress or kilt-like skirt but was worn over a conventional full-length sleeved dress (often with additional petticoats under the dress if the wearer could afford them) and so it functioned as a warm top covering or over-mantle that could also be drawn up to cover the head or used to wrap up babies close to the mother's body. The arisaid was often not tartan but was dyed a plain colour, maybe with a coloured border or simple stripes.

   

The first drawing is from 1754, so shortly after the wearing of highland dress was banned by the Dress Act of 1746 although this didn't apply to women and as her man is a soldier in British highland regiment his particular plaid is also exempt as it's part of an officially-recognised regimental uniform. The other two are from 1845 when all things Scottish were starting to enjoy a revival, but are reconstructions based on written descriptions of about 150 years earlier. I think strictly the lass on the right isn't wearing a full arisaid but rather a simpler plaid shawl known as a tonnag.

The point to note is that they are all wearing conventional (for the time) long skirts under their over-mantel, and that again none of these women are actually wearing kilts.