sleeves or partlett.
This is a stripe, similar to many of the embroidered chemise/smocks/shirts from the 16th century. Generally the stripe is longways on the arm and body and goes from front to back on partletts. This design is not suitable for cuffs or coifs and too light for a forepart. IT might work on a very narrow ruffle, but keep coming back. I'm working on a version set up for that!