Webster's 1913 Dictionary
SWAN'S-DOWN; SWANS-DOWN
SWAN'S-DOWN; SWANS-DOWN Swan's "-down `, or; Swans "-down `, n.
1. The down, or fine, soft feathers, of the swan, used on various articles of dress.
2. A fine, soft, thick cloth of wool mixed with silk or cotton; a sort of twilled fustian, like moleskin. Swan's-down cotton. See Cotton flannel, under Cotton.
Sanseido Wisdom Dictionary
swan's-down
sw á n's-d ò wn sw á ns d ò wn 名詞 U 1 白鳥のわた毛 〘へり取り パフ用 〙.2 (ベビー服など用の )柔らかい生地 .
The Wordsmith Dictionary