Irish costume research is not as easy a task as Italian or English, for example, because of the rarity of illustrations. The Irish are traditionally an oral culture. While their musical and narrative legacy is rich, the society provides us with little concrete evidence. Writing was not used until the introduction of Christianity. The art of painting was never pursued in any real fashion. Even in the writings we do possess, the Irish do not give the kind of detail we have come to expect from Roman writers for example. This can be explained by the fact that Irish writers were writing for themselves who understood the cut of the clothing and detail was not necessary. The Romans, by contrast, were describing foreign styles from the provinces to an audience at home.

Luckily we have more than one place to look for information on Irish clothing. The Highlands of Scotland had connections with Irish from very early times, some inhabiting parts of Argyll. Dalriada was the name of the people who came from Ireland and whom the Romans called the Scots. The earliest knowledge we have of them comes from when they were still in Ireland. At that time there were four septs or main families of the Erainn stock. A famine occurred and made it necessary for some of the septs to emigrate. A portion of Dal Riata remained in Ireland while Cairpre Riata led the rest of his people across the water to the land of the Picts. Cairpre Riatalanded with his people in Scotland yet the Kingship of Dal Riata stayed in Ireland. This remained the case until Fergus mor Mac Erc, King of Dal Riata, arrived with more of his people bringing his Kingship with him and in doing so shifting the emphasis of Dal Riata from Ireland to Scotland. Eventually the Irish Dal Riata became a separate entity, although the two were still allied. When considering modern history, it does not seem that the Scottish and Irish would be related at all. Yet only a glance at their language, customs or traditional clothing would tell different. Scots and Irish Gaelic, though technically two different languages, are mutually intelligible. Though of two different Christian practises, the Irish and Highland Scots hold many of the same folk traditions. And though the Irish never developed the kilt, the use of brightly coloured woollen mantles and saffron shirts was identical in Ireland and the Highlands.

There is much debate about what the léine was and was not. Léine is simply the Irish word for "shirt." The ancient Irish used it for what they wore. The modern Irish use it to mean everything from dress shirt to T-shirt. Therefore, the garment thus labelled is not unique.

In clothing research, the name has come to be synonymous with the 16th century “saffron shirt" of the Irish and Highland Scots. It is in this context that we call the garment the "Man's Léine."

The first evidence we have for the 16th century léine is from a print in the Ashmolean Museum, Oxford, England. The picture is labelled "Irish Chieftains." No other copy exists and nothing is known about its origin. From other evidence it appears to have been drawn in the reign of Henry VIII. Some have conjectured that it depicts some of Henry's Irish recruits for his war with France in 1544. The details of this print are carefully drawn. A note on the border of the drawing claims that it was drawn from life as opposed to from memory (it is labelled: "after the quick" meaning "from life").

The men depicted in this print are all wearing long tunics with wide hanging sleeves and short, elaborately decorated jackets. Some wear mantles. All carry swords. All are similarly barelegged and bare-footed. They are Irish kern(catharnach) or non-professional infantry soldiers of the Tudor period. From the consistency of their dress, we can assume these garments were commonly worn in battle. The same full tunic with hanging sleeves and short jacket is shown in prints dated 1547 and 1575 by Lucas De Heere. Again it is worn with a short leatherjacket by an Irish kern. In one print, a piper also wears this garment, though his has red embroidery around the sleeves. Pipers, however, were normal participants in Irish armies and therefore this depiction of a musician wearing military dress is not unusual.

Though poorly drawn, John Derricke's Images of Ireland shows the same outfit. This time, the subject is a courier delivering a message to an English lord. "Runners" were also members of Irish armies and would be dressed similarly to soldiers.

An engraving in the first edition of Holinshed's Chronicle (published 1577) shows léine-clad Scots bow-hunting deer in the mountains. They wear the same elaborately decorated, short, leather jacket over long, full tunics. The tunics are obviously bloused over a belt. The sleeves dangle to the knees or calves, but do not come any lower on the arm than the elbow joint. This representation of hunters clearly demonstrates the reason for the sleeve construction. The sleeves do not appear to hinder the bowman in any way. Neither to they appear to encumber the kern in the earlier prints. This was the Irish/Scottish way of making a fashion statement (and a statement of wealth as well) while not sacrificing functionality.
Where did such a strange looking garment come from? We know that nothing develops in a vacuum. And even in remote Ireland, fashions were influenced by the clothing of other peoples. Wide and flowing floor-length garments, extravagant sleeves, pleating to excess — these are all typical of the houppelandes of the previous century. From stone effigies in Ireland, we know that at least the Anglo-Irish ladies of the 15th century wore the houppelande. Léinte in the 16th century we reputedly made with 25-35 yards of linen. The Irish simply modified the continental style to suit their own tastes. The Irish were often criticized for dressing above their station. Henry's 1537Act for the Common Order sought to reduce the volume of fabric used in the léinte to a mere 7 yards to discourage such impropriety. Yet the poor Irish routinely sacrificed their livelihoods to wear the best clothes, the fairest cuts, and the most fabric.
The houppelande was court dress, not a military garment. How did it come to be worn by Irish kern? Quite simply, it became utilitarian. 25-35 yards of linen "pleates on pleats thei pleated are as thicke as pleats maie lye" (John Derricke, Images of Ireland, 1577) makes for excellent protection against almost anything, even sword blows. For a self-funded kern fighting without armour, the léine was literally the only thing between him and death.

On tomb effigies of the 14th century, we see thickly pleated gambesons called cotún. They were made of linen and stuffed with scraps for padding. This gambeson protected the noble warrior from the "bites" of his own coat of mail. It also protected the less wealthy soldier from sword blows.

Conjecture has been made that the Scots and Irish léine croich and the gambesons depicted in tomb effigies are the same garment. Although they are related garments serving the same function, they are not one and the same.

For proof, we must look at the contemporary writings regarding the saffron shirt. In all these accounts, the word used to describe the léine is "shirt"(shift, camisa, chemise, etc.). Yet three writers mention something else. John Major in his 1521 History of Britain speaks of both a "shirt" (camisa) and a "manifoldly sewed linen garment" (panno lineo) worn in battle:

"A medio crure ad pedem caligas non habent, chlamyde pro veste superiore et camisa croco tincta, amiciuntur...Tempore belli loricam ex loris ferreis per totum corpus induunt ei in illa pugnant. In panno lineo multipliciter iintersuto et coerato aut picato cum cervinae pellis coopertura vulgus sylvestrium Scotorum corpus tectum habens in praelium prosilit." "From the middle of the thigh to the foot they have no covering for the leg, clothing themselves with a mantle instead of an upper garment and a shirt dyed with saffron...In time of war they cover their whole body with a shirt of mail of iron rings, and fight in that. The common people of the wild Scots rush into battle having their body clothed with a linen garment manifoldly sewed and painted or daubed with pitch, with a covering of deerskin."

The History of the Gordons mentions "...cloathed in a yellow warr coat (which amongst them is the badge of the Chieftains or heads of Clans)..."And Robert Gordon of Straloch writes of their war and peace apparel as if speaking of two separate garments:

"As for their Apparel; next the Skin, they wear a short linnen Shirt, which the great men among them sometimes dye of saffron colour. They use it short, that it may not encumber them, when running or travelling. Major says the common people among them went out to Battle, having their Body covered with Linnen of many folds sewed together and done over with Wax or Pitch, with a covering of Hart's skin; but that the English and common Lowland Scots fought in Clokes."

These passages indicate that the léine or saffron shirt and the cotún orgambeson were two different garments.

For further substantiation, we will move to the physical evidence. On Irish and Highland tomb effigies we see depictions of quilted gambesons with tight sleeves sometimes worn under a mail halberk. The identical garment can be seen on the Burke tomb effigy at Glinsk in County Galway, the O'Cahan tomb at Dungiven in County Derry and in all the Highland tomb effigies. However, in none of these effigies are the characteristically long sleeves of the léine portrayed. All the carvings have distinctly tight sleeves and none show anything resembling a short jacket.

In the illustrations of the léine, as we have already discussed, the garments always have long sleeves and flowing skirts and are worn with short jackets, ionar. Contemporary writings indicate that the jackets were thrown off in battle. Yet the léine is never shown without one.

We must conclude that the léine croich was a voluminous shirt worn in battle by Irish kern and Scottish Highland soldiers. These garments were made of as much linen as the wearer could afford. He would wear it as heavily pleated as possible to provide him better protection. Those who could afford shirts of mail wore them over a kind of padded jacket. In those cases sleeves were fitted so that they could fit through the mail shirtsleeves. This was a different garment altogether, known as a cotún.