I don’t know a name for it but here is what I would do. Put the zipper in using the fashion fabric on say the left and on the right use a piece of muslin. I know this looks weird. Then take a piece of fashion fabric and clean finish the end (serge or zigzag). fold it under about 3 inches. Lay it on top of your half fashion fabric, half muslin back of the pillow so it covers the zipper completely. Pin in place and then cut the piece so it will be the proper square size for the back of the pillow. So on the left side you have fashion fabric , then the installed zipper, then on the right you have fashion fabric covering the zipper with a fold and underneath is a muslin that attaches to the right side of the zipper. HTH, Bunny_________________