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Yes schiltron (or shiltron) gets Google going and is the accepted term. Probably the same root as the Anglo Saxon scild or scield meaning shield or defence together with "truma" meaning array or troop. Scildtrum is probably OK but never used in this context(source-a concise Anglo Saxon Dictionary). Defensive array sounds good which is probably what was meant by the chroniclers when they saw it.
I am not sure what this set adds to the set 081 other than the shields but then they were important but the troops are still a bit too well armoured. The Medieval Levy set 2 is good as well. I suppose all the sets together make for a mixture which is good for the period.
According to Froissart the bulk of the Scottish infantry was mounted on small ponies. A Scottish infantryman with pike/spear on a pony traveling to battle is OK though of course they dismounted for battle. They often used mounted infantry on raids. The Irish/English hobelar as a counter to this is again an important troop type missing from most all? sets.
George Gush's book "Renaissance Armies" remarks that the Scots wore yellow shirts upto about 1600 (p.44 Patrick Stevens 1982), so not really new info considering that it was originally published in 1875 and I am sure was drawing on older secondary material.
But presumably the Lowland Scots who must have made up the majority of Bruce's armies (and who weren't Gaels, and presumably eschewed those cultural trappings), would have resembled their English cousins/neighbours more closely.
Still, i suppose the point of this set from Strelets is to do something different from the more generic medievals, so, apart from the sporrans, i'm sure they'll look fine in their yellow shirts.
Taking up the 1875 tag William Morris and his followers were well aware of medieval costume, dyes and their properties so that date is probably not far off for the original source material.
One of my heroes! You are right Morris was a great admirer of medieval tradesmen and was well versed in the technologies and skills of those days. I went to school in Bexleyheath where he had a house (the Red House) which is full of textiles and painting - the walls are even gridded with small indentations in the plaster to help the unskilled produce artwork.
"..From Robert's throat he loosed the bands
Of silk and mail; with empty hands
Held out, she stood and gazed, and saw
The long bright blade without a flaw
Glide out from Godmar's sheath, his hand
In Robert's hair, she saw him bend
Back Robert's head; she saw him send
The thin steel down; the blow told well,
Right backward the knight Robert fell,
And moaned as dogs do, being half dead,
Unwitting, as I deem: so then
Godmar turn'd grinning to his men,
Who ran, some five or six, and beat
His head to pieces at their feet....."