Csák was the name of a gens (latin for "clan"; nemzetség in Hungarian) in the Kingdom of Hungary. The Gesta Hunnorum et Hungarorum ("Deeds of the Huns and Hungarians") records that the ancestor of the family was Szabolcs, son of chieftain Előd, the leader of one of the seven Magyar tribes. The family was probably connected to the Árpád dynasty. Their ancient possessions were located around the Vértes Hills in Transdanubia; Csákvár ("castle of Csák") and Csákberény villages still bear their name. The family was named after Szabolcs' grandson who had a fortress built on his possessions.
The gens divided into 12 branches and several families in the course of the centuries.
Sources
Kristó, Gyula (editor): Korai Magyar Történeti Lexikon - 9-14. század (Encyclopedia of the Early Hungarian History - 9-14th centuries); Akadémiai Kiadó, 1994, Budapest; ISBN 963 05 6722 9.