swan's-down

{ or }, n. 1. The down, or fine, soft feathers, of the swan, used on various articles of dress. [ 1913 Webster ]

2. A fine, soft, thick cloth of wool mixed with silk or cotton; a sort of twilled fustian, like moleskin. [ 1913 Webster ]

Swan's-down cotton. See Cotton flannel, under Cotton. [ 1913 Webster ]