An Etymological Dictionary of Astronomy and Astrophysics

1. Light, downy particles, as of cotton.
   

2. A soft, light, downy mass (Dictionary.com).

Etymology (EN): Apparently a variant of floow “wooly substance, down, nap,” perhaps from Flemish vluwe, from Fr. velu “shaggy, hairy,” from L. vellus “fleece,” or L. villus “tuft of hair” (Online Etymology Dictionary).

Etymology (PE): Kork “down, soft wool, fluff,” of unknown etymology.