"Couldn't remember all the goblin rebels' names, so I invented a few.... It's all right, they're all called stuff like Bodrod the Bearded and Urg the Unclean; it wasn't hard."
-- Ron to Mrs Weasley (GF31)
Urg the Unclean was a rebel leader during the goblin rebellions of the eighteenth century.
Urg was the subject of a "Famous Goblin" card (FW).
Other canon notes and references
Urg was also mentioned in the third W.O.M.B.A.T. test (which appeared on jkrowling.com in June 2007) as a possible answer to the question "Which of the following did NOT provoke one of the bloody goblin rebellions of the 17th and 18th centuries?" (JKR-W3).
According to the W.O.M.B.A.T. 3 test, Urg was a goblin activist (who might have been ducked in a pond by a gang of young wizards). Unless we get the answers to the test someday, the ducking cannot be considered canon.