The Breacan an Fhéilidh (belted plaid) or Feileadh Mòr (great plaid) is likely to have evolved over the course of the 16th century from the earlier ‘brat’ or woollen cloak (also known as a plaid) which was worn over a tunic. This earlier cloak or brat may have been plain in colour or in various check or tartan designs, depending on the wealth of the wearer; this earlier fashion of clothing had not changed significantly from that worn by Celtic warriors in Roman times.
Over the course of the 16th century, with the increasing availability of wool, the cloak had grown to such a size that it began to be gathered up and belted. The belted plaid was originally a length of thick woollen cloth made up from two loom widths sewn together to give a total width of 54 to 60 inches, and up to 7 yards (6.4 m) in length. This garment, also known as the great kilt, was gathered up into pleats and secured by a wide belt.
Plaids with beltloops were in use by the 1700s. A surviving men’s belted plaid from 1822 has belt loops sewn inside it at each pattern repeat, such that it can be unpleated entirely into a blanket, or rapidly pleated with a drawstring belt (with a second belt worn outside, to flatten the pleats, as in the portrait of Lord Mungo Murray above).
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 léine (a full-sleeved garment stopping below the waist) 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.
For battle it was customary to take off the kilt beforehand and set it aside, the Highland charge being made wearing only the léine or war shirt.
The exact age of the great kilt is still under debate. Earlier carvings or illustrations prior to the 16th century appearing to show the kilt may show the léine croich, a knee-length shirt of leather, linen or canvas, heavily pleated and sometimes quilted as protection. The earliest written source that definitely describes the belted plaid or great kilt comes from 1594. The great kilt is mostly associated with the Scottish highlands, but was also used in poor lowland rural areas. Widespread use of this type of kilt continued into the 19th century, and some still wear it today.