Tea at the Trianon, always an interesting read, has an interesting post on a legend about Lourdes and its chateau:
The Gauls, Roman, Barbars and Moors successively took turns to strengthen the Lourdes rock on which the castle stands. This antique fortress is clothed in legend. In 778, Charlemagne and his army besieged the castle which was occupied at the time by Mirat, the Saracen, and his Moors. Despite attacks by the Francs and the onslaught of famine, Lourdes castle remained impenetrable.
Suddenly an eagle appeared in the sky. It flew around the fort and dropped an enormous trout from its beak, which landed at Mirat's feet. The clever Moor grabbed the fish and took it to Charlemagne to make him believe that he still had plenty of food reserves.
Charlemagne was just preparing to lift the siege when Turpin, his friend and Bishop of Puy-en-Velay, became inspired and was granted permission to go and talk to the besieged. He suggested that Mirat surrender, not to the sovereign but to the Queen of the skies [Heaven].
This proposal pleased the Moor leader who promptly set down his weapons at the foot of the Black Virgin of Puy and was baptized. On the day of his baptism, Mirat was given the name "Lorus". This name was transferred to the village, which, in time, became Lourdes.