Wiktionary
n. 1 A small beanbag or sandbag used as a ball in a number of sports and games. It is typically controlled by the feet, but in some sports every part of the body except the hands and arms may be used. 2 A generic name for the sports which use the footbag.
Wikipedia
A footbag is both a small, round bag, and the term for the various sports played with one – characterized by controlling the bag by using one's feet. Although often referred to generically as a Hacky Sack, that is the trademarked name of one specific brand.
Footbag-like activities have existed for many years. There are documented examples like Wu Style Tai Chi Chuan practice and policemen are seen playing it using a shuttlecock in the 1955 movie To Catch a Thief, but the current Western incarnation of the sport was invented in 1972 by Mike Marshall and John Stalberger of Oregon City, Oregon with the Hacky Sack, the rights to which are now owned by Wham-O.