The dolmens of the Fountain of His attest to human occupation in Neolithic. Towards 1066 mentioned "Mons Sancti Leodegarii" then the town is named after a castle "Roche Rabasté".
Finally, it is the association of the name of the eponymous Saint "Saint Léger" and Montbrillais, the most important town until the nineteenth century, which will be retained.