One who cuts or blends; specifically, a wine merchant or blender who creates coupage.
From French 'couper' (to cut/blend) plus the agent suffix '-er' (from Old English -ere). In French, this describes someone whose job is cutting or blending wines, a specialized role in wine production.
The existence of a specific term 'couper' for wine blenders shows how specialized medieval and early modern wine production was—there were entire guilds of people whose sole job was understanding how to blend wines, making them something like the audio engineers of their era.
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