Sir Monier Monier-Williams(1898)A Sanskrit-English dictionary etymologically and philologically arranged with special reference to cognate Indo-European languages, Oxford: Clarendon Press, page 0502
Etymology
From Proto-Indo-European*drew-, oblique case stem of *dóru, whence also regularly Sanskrit दारु(dā́ru). Compare Ancient Greek δρῦς(drûs) and Old Church Slavonic дръва(drŭva).