An Etymological Dictionary of the German Language/Wolle
Wolle, f., ‘wool, down,’ from the equiv. MidHG. wolle, OHG. wolla, f.; corresponding to Goth. wulla, AS. wull, E. wool, Du. wol. Teut. wullô-, from pre-Teut. wlná (for ll from ln see Welle and voll), corresponding the Aryan languages to Sans. ûrṇâ, OSlov. vlŭna, Lith. vílna, ‘wool’; in Lat. villus, vellus. Sans. ũrṇâ is connected with a root vṛ, ‘to cover, wrap’ (pres. ûrṇõmi); hence Welle (Aryan wlnâ) meant lit. ‘that which covers.’ Gr. εἰρος, ἔριον, ‘wool,’ cannot be related to the common Aryan cognates (root wel).