Wiktionary
swan's down
n. (alternative spelling of swansdown English)
WordNet
swan's down
n. soft woolen fabric used especially for baby clothes
down of the swan
Usage examples of "swan's down".
They opened and spread, fanlike, behind him: two more kite-shaped forms like giant scapulae covered in swan's down and white eagle's feathers.
The mortals walked forward into a pallor wherein minuscule motes drifted like swan's down.