Known as shirring. Even so, the glimpse it results in is very similar to smocking, which is an embroidery method that’s been around an extended while. But possibly don’t google “what exactly is smocking” cuz apparently it also refers to a thing that has almost nothing to perform with sewing… https://doublecoveredyarn74948.pages10.com/rumored-buzz-on-rubber-covered-yarn-67196881