Saint-Thierry
Early Christians started the custom of celebrating martyrs on their passing anniversary and that's how the French calendar filled up with names of saints and of course Christian Holidays.
Saint-Thierry was apparently the son of a bandit who discovered his monastic calling on the day of his marriage! The marriage was therefore annuled and he retired near Reims in the Champagne region where he founded a monastery later named after him.
In the early 500's, Thierry the monk became known for performing miracles. As a strange coincidence would have it, he healed the eye of a man with the same name! The other man was Thierry I, then King of the Franks, since his father Clovis had divided his kingdom among his sons...