The word “Cathar”, meaning “pure”, is of Greek origin and designates the dualist heretics who made their presence felt in the West in the second half of the 11th century. The oldest document mentioning it is a deed issued by Nicolas, Bishop of Cambrai (1164-1167), which records the condemnation of a cleric, Jonas, “convicted for being a Cathar heretic”, pronounced by the Bishops of Cologne, Treves and Liège between 1151-1152 and 1156.