Learned borrowing from Latin vellus (“fleece”).

vellus (plural vellera)

1. The stipe of certain fungi.

• villus

Traditionally derived from Proto-Indo-European *h₂welh₁- (“hair, wool”), and connected to Latin lāna (“wool”) and Gaulish vlana.^[1] This is favored by Meiser, but rejected by Schrijver and De Vaan, the latter who instead proposes the word as a derivative of vellō (“to pluck out”).^[2]

• (Classical Latin) IPA^(key): [ˈwɛl.lʊs]
• (modern Italianate Ecclesiastical) IPA^(key): [ˈvɛl.lus]

vellus n (genitive velleris); third declension

1. The wool shorn from a sheep; fleece; wool
2. The hide or pelt of an animal
   • 8 CE, Ovidius, Fasti 4.765–766:

     ‘nēve minus multōs redigam, quam māne fuērunt,
     nēve gemam referēns vellera rapta lupō.’

     ‘‘And may I never drive back fewer [sheep] than there were in the morning,
     and may I never groan as I bring back hides snatched from the wolf.’’
     (A shepherd’s prayer to Pales.)

Third-declension noun (neuter, imparisyllabic non-i-stem).

• (wool): lāna

• From vellus, vellum (merged with villus):
  • Italian: veglio, vello
  • Portuguese: velo
  • Sicilian: veḍḍu
• From *vellus, vellōrem > *vellō, vellōnem:
  • Catalan: velló
  • Spanish: vellón

• “vellus”, in Charlton T. Lewis and Charles Short (1879), A Latin Dictionary, Oxford: Clarendon Press
• “vellus”, in Charlton T. Lewis (1891), An Elementary Latin Dictionary, New York: Harper & Brothers
• "vellus", in Charles du Fresne du Cange, Glossarium Mediæ et Infimæ Latinitatis (augmented edition with additions by D. P. Carpenterius, Adelungius and others, edited by Léopold Favre, 1883–1887)
• “vellus”, in Gaffiot, Félix (1934), Dictionnaire illustré latin-français, Hachette.