Identified as shirring. Having said that, the look it creates is similar to smocking, and that is an embroidery procedure that’s been around an extended long time. But maybe don’t google “what is smocking” cuz seemingly it also refers to a thing that has practically nothing to accomplish with sewing… https://double-covered-yarn65320.mybloglicious.com/52371948/the-ultimate-guide-to-covered-spandex-yarn