Description from Knitty.com:

My version of these liberating Unmentionables is based on the more elaborate frillies worn during the Edwardian period. They are knit entirely in the round. Each leg begins separately with a crochet-chain provisional cast on and then crotch stitches are set aside (to be grafted later) before the legs are joined and the body is knitted up to the low-rise waist. Then stitches for each leg are picked up and the ruffle and lace edging are knitted downward. Don't let the piquant label put you off; once you brave the provisional cast on, the most challenging part is the lace edging. Whether you wear them as summer outerwear or loungewear, do give a nod to the forward-thinking ladies of days long past.