noun
goose down; goose feather
Refers to the soft feathers or down of a goose, often used for filling bedding or clothing.
この布団には上質の鵞毛が使われている。
This futon uses high-quality goose down.
羽毛 is a general term for feathers or down of any bird, while 鵞毛 specifically refers to goose down/feathers.
Compound of 鵞 (ga, 'goose') and 毛 (mō, 'hair/feather'). The exact historical derivation is uncertain, but the spelling is conventionally associated with goose down.