Фасмер 1,293

Old East Slavic вьрба, Belarusan вярба, (dialectal) вэрба, Ukrainian верба, Old Church Slavonic вьрба, Bulgarian върба, Macedonian врба, Serbo-Croatian вр́ба, vŕba, Slovenian vŕba, Old Czech vrba, Czech vrba, Moravian (Mistřice) vŕba, Polabian varbă, Old Polish wierzba, Polish wierzba, Silesian wiyrba, Slovak vŕba, Upper Sorbian wjerba, Lower Sorbian wjerba

Фасмер I, 306. From Proto-Slavic *větvь 'branch'; cognate with Old East Slavic вѣтвь, Bulgarian ве́тва (vétva), ве́тка (vétka), ве́я (véja), and ве́йка (véjka), Slovenian vȇja, Czech větev, Slovak vetva, Ukrainian ві́та 'branch, twig', from Proto-Indo-European *uh₁i-tu-s Latin vītis 'vine', German Weide 'willow', Ancient Greek ἴτῠς 'felloe', Old Prussian witwan 'willow', Persian bid 'willow', and English withe 'twig or shoot'

Derksen 2008 522, Kroonen 2013, 568, De Vaan 2008, 677
Mallory, J. P., Adams, D. Q. (2006), The Oxford Introduction to Proto-Indo-European and the Proto-Indo-European World (Oxford Linguistics), New York: Oxford University Press, page 167
Beekes, Robert S. P. (2010) Etymological Dictionary of Greek (Leiden Indo-European Etymological Dictionary Series; 10), volume I, with the assistance of Lucien van Beek, Leiden, Boston: Brill, page 605