Sock

From Conservapedia

A sock is usually one of a pair of knitted garments worn on the feet (one per foot) in order to ease chafing between the foot and shoe, and to keep the feet warm. Socks are of some antiquity. Knitted socks have been excavated from the Viking city of York and are on display at the Yorvik Centre there.

A sock in more modern terms can refer to an internet user who uses more than one user ID to log onto a site.