A onesie (/ˈwʌnzi/) is a type of loose-fitting casual jumpsuit in adult sizes made of knit cotton (as used in sweatshirts), fleece, or chenille.[1] They were mostly intended as loungewear or sleepwear, but have gained significant popularity as stylish streetwear, especially in the United Kingdom and Australia, becoming increasingly popular during the late 2000s and early 2010s as a street fashion. In 2016 the onesie also appeared in Switzerland. After onesies lost importance, in the UK the onesie made a comeback in the 2022 energy crisis to save heating costs as a warm and comfortable garment.[2]