E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Master of the rain. St. Médard was the founder of the roseprize of Salency in reward of merit. The legend says, he was one day passing over a large plain, when a sudden shower fell, which wetted everyone to the skin except himself. He remained dry as a toast, for an eagle had kindly spread his wings for an umbrella over him, and ever after he was termed maître de la pluie.