What is the difference between assemblage and coupage?

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Dear Dr. Vinny,
What is the difference between assemblage and coupage?
—Franco S., Playa del Carmen Mexico
Dear Franco,
Not much. Both are French words that refer to blending wine before bottling.
Splitting hairs, coupage has an ever so slight negative connotation, since it translates literally into something like “to cut” and can indicate stretching out a good wine by cutting it with lesser-quality wine, while assemblage sounds more like you’re creating a fine bottle of wine by putting all the pieces together. But the terms are really used interchangeable, with assemblage being more common.
—Dr. Vinny