They are often worn at weddings or other formal occasions, while there are still a few people who wear them daily. Kilts are also used for parades by groups like the Boy Scouts, and in many places kilts are seen in force at Highland games and Pipe band championships as well as being used for Scottish country dances and ceilidhs. The army still continues to have kilts as dress uniform, though they are no longer used in combat. The Garment's name comes from the Scots word kilt meaning to tuck up the clothes around the body.
The Great Kilt
The Fèileadh Bhreacain or Fèileadh Mor was originally a length of thick woollen cloth made up from two loom widths sewn together to give a total width of 1.5 m, up to 5 m in length. The great kilt, also known as the belted plaid, was an untailored draped garment made of the cloth gathered up into pleats by hand and secured by a wide belt. The upper half could be worn as a cloak draped over the left shoulder, hung down over the belt and gathered up at the front, or brought up over the shoulders or head for protection against weather. It was worn over a leine (or shirt) and could also serve as a camping blanket. A description from 1746 states:
"The garb is certainly very loose, and fits men inured to it to go through great fatigues, to make very quick marches, to bear out against the inclemency of the weather, to wade through rivers, and shelter in huts, woods, and rocks upon occasion; which men dressed in the low country garb could not possibly endure." In battle it was usual to take off the kilt beforehand and set it aside, the Highland charge being made wearing only the leine.
The age of the great kilt is hotly debated but it certainly existed at the beginning of the 17th century. Earlier carvings or illustrations appearing to show the kilt may show the Leine Croich, a knee-length shirt of leather, linen or canvas, heavily pleated and sometimes quilted as protection. The great kilt is mostly associated with the Scottish highlands, but was also used in poor lowland rural areas. Use of this type of kilt continued into the 19th century.
Origins of the Modern, or "Small Kilt"
Sometime early in the 18th century the fèileadh beag or philabeg using a single width of cloth hanging down below the belt came into use and became quite popular throughout the Highlands and northern Lowlands by 1746, though the great kilt also continued in use.
A letter published in the Scots Journal in March 1785 argued that the garment people would today recognize as a kilt was invented around the 1720s by Thomas Rawlinson, a Quaker from Lancashire. Rawlinson is claimed to have designed it for the Highlanders who worked in his new charcoal production facility in the woods of northern Scotland. After the Jacobite campaign of 1715 the government was "opening" the Highlands to outside exploitation and Rawlinson was one of the businessmen who took advantage of the situation. He thought that the traditional Highland kilt, the "belted plaid" which consisted of a large cloak, was inconvenient for tree cutters and introduced the new kilt. Rawlinson liked the new creation so much that he began to wear it as well and was soon imitated by his Scottish colleagues, the MacDonell's of Glengarry.
The Early History of the Kilt (http://albanach.org/kilt.html) and Reconstructing History (http://www.reconstructinghistory.com/scottish/18thckilt.html) quote modern scholarship disputing this story with reference to earlier illustrations of the small kilt.
Military use and proscription
From 1624 the Independent Companies of Highlanders had worn kilts as government troops, and with their formation into the Black Watch regiment in 1740 their great kilt uniform was standardised with a new dark tartan. After 1745 the Government decided to form more Highland regiments for the army in order to direct the energies of Gaels, that "hardy and intrepid race of men". In doing so they formed effective new army regiments to send to fight in India, America, and other locations while lowering the possibility of rebellion at home. As a means of identification the regiments were given different tartans. These regiments opted for the modern kilts for dress uniforms, and while the great kilt remained as undress uniform this was phased out by the early 19th century.
In 1746 after the last Jacobite campaign the "Dress Act" outlawed all items of Highland dress including the new kilts (with an exception for army uniforms). The ban remained in effect for 35 years. and the traditional way of life throughout the Highlands was destroyed.
The revival of the kilt
Although the kilt was largely forgotten in the Scottish Highlands, during those years it became fashionable for Scottish romantics to wear kilts as a form of protest against the ban. This was an age that romanticized "primitive" peoples, which is what Highlanders were viewed as. Most Lowlanders had viewed Highlanders with fear before 1745, but many identified with them after their power was broken. The kilt, along with other features of Gaelic culture had become identified with Jacobitism and now that this had ceased to be a real danger it was viewed with romantic nostalgia. Once the ban was lifted in 1782 Highland landowners set up Highland Societies with aims including "Improvements" (which others would call the Highland clearances) and promoting "the general use of the ancient Highland dress". The Celtic Society of Edinburgh, chaired by Walter Scott, encouraged lowlanders to join this antiquarian enthusiasm.
The kilt became identified with the whole of Scotland with the the pageantry of the visit of King George IV to Scotland in 1822, even though 9 out of 10 Scots lived in the Lowlands. Scott and the Highland societies organised a "gathering of the Gael" and established entirely new Scottish traditions, including Lowlanders wearing the supposed "traditional" garment of the Highlanders. At this time many other traditions such as clan identification by tartan were developed.
After that point the kilt gathered momentum as an emblem of Scottish culture as identified by antiquarians, romantics, and others, who spent much effort praising the "ancient" and natural qualities of the kilt. King George IV had appeared in a spectacular kilt, and his successor Queen Victoria dressed her boys in the kilt, widening its appeal. The kilt became part of the Scottish national identity.
The Kilt Today
Kilts have become normal wear for formal occasions, for example being hired for weddings in much the same way as top hat and tails are in England or tuxedos across the pond, and can be worn by anyone regardless of nationality or descent.
The modern tailored kilt is box-pleated or knife-pleated, with the pleats sewn in and the lower edges reaching not lower than the centre of the knee-cap. Nowadays a lighter weight of cloth tends to be used. The kilt is traditionally for men only, although in the modern era, long women's dresses patterned after kilts do exist, and women pipers frequently wear kilts. Kilten skirts for girls are also worn.
As with any other form of dress, the kilt is subject to the vagaries of fashion. Since the 1980s, kilts have appeared in such materials as leather and denim. Single colours have also been used in place of tartan, particularly by people without Scottish links in countries such as Ireland or the United States. While these garments may be disliked by traditionalists, they provide evidence that the kilt still has a place in the modern fashion world.
As a kilt has no pockets, it is worn with a pouch called a sporran. Originally this was a soft deer skin pouch, but with the development of military uniforms elaborate hard leather sporrans came into use, often with decorative silver tops and white hair facings with large tassels. A decorative silver kilt pin adds weight to the loose bottom corner of the kilt.
A small dagger called a Sgian Dubh may be worn in the tall stockings which form part of the standard clothing worn with a kilt. Shoes are usually leather brogues, sometimes with open lacing.
Nowadays a special jacket is usually worn with the kilt. This is often in green tweed, but with the kilt as formal dress a black "Prince Charlie" jacket is usual.
With some full dress uniforms a plaid is added in the form of a pleated cloth in the same tartan as the kilt, cast over the shoulder and fastened at the front with a plaid brooch.
A good rule of thumb is that kilts should be worn without underwear in daily use, but with it for dancing (when a light kilt may fly up). In practice, underwear is not needed for a fully lined kilt, but may be preferable for an unlined woollen kilt to prevent chafing. In the end whether or not underwear is worn on any particular occasion, is up to the weather, the company, and the individual wearer.
Whatever decision is made, what a Scotsman wears under his kilt is, traditionally, his own business and generally, Scotsmen will be at pains to keep it so. Thus the reply to a question on the topic may hint at the answer but should never state it outright. A good standard reply when asked, is that, "Nothing is worn under the kilt. It's all in perfect working order".