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This winery shares a part of its name with Château Grand-Puy-Lacoste. Grand Puy is the name of a low gravelly hill which used to be owned in its entirety by the same estate. Parts of the vineyards on this hill were sold in 1750 to a man by the name Pierre Ducasse, which was the origin of the name.
References
MacNeil, Karen, (2001). The Wine Bible, Workman Publishing, pp. 885, ISBN1-56305-434-5