Called shirring. Even so, the glimpse it makes is similar to smocking, and that is an embroidery approach that’s existed a protracted while. But possibly don’t google “precisely what is smocking” cuz apparently Furthermore, it refers to something that has nothing to perform with sewing… In any case, shirring Polymerization: https://coveredspandexyarn00975.answerblogs.com/31865124/the-ultimate-guide-to-smoking-thread