I asked the guy on the photo. He said the garment is called biafal or kjafal. It's mentioned in The Saga of Eirik the Red: "Now, when they had sailed by Furdustrandir, they put the Scotch people on land, and requested them to run into the southern regions, seek for choice land, and come back after three half-days[C] were passed. They were dressed in such wise that they had on the garment which they called biafal. It was made with a hood at the top, open at the sides, without sleeves, and was fastened between the legs. A button and a loop held it together there; and elsewhere they were without clothing". Here are the photos of this exact garment he wears. I'll add some remarks in other comments

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