A medieval tailor wasn’t a fabric merchant. They took the fabric the customer brought, and made the desired garments. Part of the details in extant tailor’s books give how much cloth should be purchased for each type of garment. The sketches showed the best way to cut the cloth, so the customer did not feel cheated. Because these late period garments are fitted, and not rectangular construction, there is SOME waste.
You can see in this example sketch from Alcega, there IS some waste. What happened to that?
I’ve been told that the rule was the tailor kept the waste bits, and it was called the cabbage. In our focus image, there is a box under the cutting table, which appears to have a jumble of fabrics in it. I think that is full of cabbage.
The tailor could then use the cabbage to fill in a needed bit on another garment. Sometimes on close inspection, we find the extant gowns have sections with multiple fabrics pieced together.
An image of one possible way to use the cabbage is part of the Polish pattern book is here. They have lots of other useful links on that site.
The tailor could also use that waste for various fabric accessories, like tasseled drawstring pouches. And thus, recycling is not a new thing.