Hi! That's an interesting topic, I tried to find some info on shaggy mantles myself, and here's what info I gathered:
For early medieval period the woven cloth with 'fake fur' appearance was quite widely known. There are examples from: Swedish Birka and Lund, Polish Wolin, Leens and Dokkum in Netherlands, Isle of Man, Isle of Eigg, York, Dublin, Heynes Farm in Iceland - so all the areas where one would need protection from cold weather.
There is a paragraph on this subject in the Aspects of the Wool Textiles from Viking Age Dublin by Frances Pritchard: ' A heavier 2.2 twill with warp and weft yarns of contrasting colour, spin and thickness has traces of a long shaggy pile. The pile matches the colour of the weft which microscopic analysis shows is natural dark brown wool while the warp is a reddish-brown hue dyed with a vegetable substance that has yet to be identified. The locks of pile, S-spun like the weft, appear to have been woven in after every four weft throws in a similar manner to that recorded on two clothes dating to around the 10th or 11th century from a farmstead at Heynes in south west Iceland. This means that each lock of pile was placed in the shed passing under six ends and then looped back round two ends; like other piled weaves produced at this period, the pile can only be seen on one side of the cloth. Literary descriptions indicate that colourful cloaks with a curly, fleece-like pile were frequently worn by men and women in early medieval Ireland, and cloaks ot this type have been recorded from the graves of Viking warrior/farmers on the nearby Isle of Man and Isle of Eigg. Further away within the Viking empire, colourful cloaks with pile were found in at least three graves at Birka, Sweden, and fragments from deposits dating to the 10th and 11th have also been noted from York, England, Lund, Sweden and Wolin, Poland. Another example is the so-called 'mantle of St Brigid', a reverend Irish saint. By tradition, this was taken to Bruges in Flanders by Princess Gunhild, a daughter of Earl Godwin and sister to Queen Edith, wife of Edward the Confessor, and King Harold, who stayed with Dermot, King of Leinster, in 1051 while raising a force of ships and men. These cloths reveal differences in weave – tabby, 2.2 twill, including broken lozenge twill, and 2.1 twill have been identified – and differences in the twist of pile and method by which it was inserted; clearly their production was not standarised, and this also applies to piled fabrics in England in the 6th and 7th centuries. The similarity of the Dublin and Iceland piled cloths is striking and it provides tangible evidence of the link that existed by the sea between the two Viking colonies, a route referred to in Eyrebyggernes saga. While the origin of the Dublin fragment is at present uncertain – both Ireland and Iceland were renowned for shaggy cloaks - the use of an uncommercial red dye rather than madder points to a rural production centre.'
More about history of piled clothes in Ireland can be found in the article “An Irish ''Shaggy Pile'' Fabric of the 16th Century – an Insular Survival?” by Elizabeth Wincott Heckett:
'Cloaks, capes and mantles of shaggy pile appear to have played an important part in Irish dress for considerable period of time. It is not clear when the first pile clothes were produced in Ireland. When information becomes available on export, there is, for example, from Cork, an item listed in 1284 for falinga, the Irish word for particular kind of cloak. This may as well describe a shaggy pile mantle. In 1354 in the Accounts of the Archbishop of Bordeaux the sum of 3 florins was spent on the purchase of ''a mantle of Ireland''. However, monkish chroniclers of the 11th 12th century settling down the oral traditions of an earlier Ireland give details of the clothes worn (presumably mirroring those of their own time). Curly fleece mantles are often described. In the story or “The Destruction of Da Derga's Hostel” the dress of Etain, the heroine is described in these terms ''There was a crimson cloak of beautiful, curly fleece around her, fastened with a silver broach coiled with lovely gold.” Later in the same story the woman called Cailb is said to be wearing “a very fleecy, striped mantle.” Again, a man seen in a vision in this tale who is a steward in a king's household wears “a very fleecy cloak”. Similarly three youths wear cloaks “as feecy as a ram” and another man “a fleecy crimson cloak”. The material for such cloaks might be similar to the remains found at Viking Age sites like Kildonan, Isle of Eigg, Birka, Sweden, Springhill, Rogart, Sutherland, Scotland and York, England. (This last reference is two pieces in which the pile has been inserted by hand afer weaving rather than being an integral part of manufacture.) A possible early Irish example isthe relic known as the mantle of St. Brigid. This piece is now in Belgium but is believed to be of Irish origin dating to the 11th century rather than the 6th, the presumed lifetime of the Saint. The textile is red in colour and is described as having a thick curly fleece woven in with either the warp (probably) or the weft.
Dr A.T. Lucas, the distinguished Irish scholar has described ways of napping cloth used in Ireland to create a curled pile. These continued until recently and included the use of teaselsto brush up the nap. In pre-industrial days drops of honey were sprinkled on the cloth and then the surface was rubbed up with a bag of small stones so that the wool was twisted into curls. Lucas believes that the pile on the St. Brigid mantle was produced in this way and that other Irish shaggy cloths would also have been finished thus.
As mentioned in both of them articles, remains of pile weave were found in Iceland – and shaggy cloaks were described in the Icelandic law code known as Grágás (12th century). As a product being traded abroad, they had standarised size “four thumb-ells long and two broad” (160x80cm), and 'could be undyed grey, white or black, or dyed red and blue; they could be plain or striped, and could be decorated with bands.' (Info after Thor Ewing Viking Clothing)
And just some additional info about other examples of pile weave known: the Polish example from Wolin is 9th century dated, 2.2 twill, 4 threads per cm for both warp and weft, locks of fleece are interwoven after every second weft. In Wolin some other textiles with threads (and not fleece) loosely inserted into the cloth ,as well as carpets were found (Info after Nahlik A."Tkaniny wykopaliskowe z wczesnośredniowiecznego Wolina", Materiały Zachodniopomorskie, tom 5., 1959
In the examples from Neterlands (found in Leens and Dokkum) long strands of s-spun thread (again not just fleece) are worked into the fabric and hanging from the surface, while the weaves are rather coarse, very thick and densely felted z/s 2/2 twills. (Info after: Chrystel R. Brandenburgh Early medieval textile remains from settlements in the Netherlands. An evaluation of textile production http://dpc.uba.uva.nl/jalc/02/nr01/a02
There is also a whole chapter of Anglo-Saxon pile weave, both with inserted threads and raised nap in Cloth and Clothing in Early Anglo-Saxon England AD 450-700 by Penelope Walton Rogers.
And as for how such a weave cold be used – definitely for cloaks (The remains of a ruggy cloak were found on the cloak pin from Birka grave Bj. 736 Thor Ewing, ibidem) but an item with inserted pile from Rogart was a shirt: (after Audrey S. Henshall Early Textiles found in Scotland http://archaeologydataservice.ac.uk/cat ... 01_029.pdf
) and in an article by Carolyn Priest-Dorman Trade Cloaks: Icelandic Supplementary Weft Pile Textiles http://www.vikinganswerlady.com/FTP_Fil ... rticle.pdf
the Hedeby fragment is mentioned: 'tenth-century Fragment 19B from Hedeby, Denmark. It was dyed with madder and
sewn to a man’s jacket garment—perhaps the only medieval instance of pink fake fur trim”.
I made a shaggy cloak for Eryk of two modern flokati rugs, worked quite well