This paper examines the increasing use of the word 'heresy' after the turn of the millennium, whether it's aimed at describing 'Manichean' (pre-Cathar ?) heretics or simply church-reformers, without neglecting the depiction of more ancient heresies (such as Arianism) in more ancient sources. Did Aquitanian historians and hagiographers write a lot about heresy before the major event represented by the Albigensian crusade at the beginning of the 13th century?