[2] In the tenth or eleventh century,[3] a Latin hagiography, the Vita sancti Willelmi, was composed.

In the chansons, he is nicknamed Fièrebrace (fierce or strong arm)[4] due to his apparent strength and the marquis au court nez (margrave with the short nose) as the result of an injury suffered in battle with a giant.

William was born in northern France in the mid-8th century, to Thierry IV, Count of Autun, and his wife Aldana.

In 788, Chorso, Count of Toulouse, was captured by the Basque Adalric, and made to swear an oath of allegiance to the Duke of Gascony, Lupus II.

In 801, William commanded along with Louis, King of Aquitaine a large expedition of Franks, Burgundians, Provençals, Aquitanians, Gascons (Basques) and Goths that captured Barcelona from the Ummayads.

William mentioned both his family and monastery in his will:[8] his will of 28 January 804, names his wives Cunegonde and Witburgis, his deceased parents, Theodoric/Thierry and Aldana, two brothers, Theodino and Adalelmo, two sisters, Abbana and Bertana, four children, Barnard, Witcher, Gotzelm and Helimburgis, and a nephew, Bertrano.

So many pilgrims were attracted to Gellone that his corpse was exhumed from the modest site in the narthex and given a more prominent place under the choir, to the intense dissatisfaction of the Abbey of Aniane.

A number of forged documents and assertions were produced on each side that leave details of actual history doubtful.