Duvets are loosely quilted featherbeds with roots originating in Europe as far back as the 14th century. Duvets were such prized possessions that they were included in wills to be passed on to the next generation. Originally, the feather blanket was called the duvet, but that language has evolved through time. In the United States, the inside is called a down comforter and the duvet refers to the cover.
The duvet cover was used to cover feather or down bedding that was especially valuable for keeping warm during the night in cold European winters. It was considered a luxury and was a way that they could use the resources they had, such as duck and goose feathers, to make bedding.
It is important to air out a feather bed in order to keep it fresh. In European countries, such as Germany and Switzerland, the people traditionally would hang their mattress in their window to air it out. In New York, during the 19th century, you could find immigrants doing the same practice in immigration quarters. One housekeeping book from the 1800s called for feather beds to be opened and feathers washed and waxed every three years.