If your brain just entered a state of confusion while reading that term, you’re not alone. (In fact, several Refinery29 staffers asked me to repeat myself when I pitched this story.) Half ordinary jeans, half leg warmers that your mom wore in the ‘80s to work out to Jane Fonda videos, these contraptions — mostly made from upcycled denim — have circulated on TikTok since January, but have picked up more popularity over the last few weeks.