Proto-Indo-European *deru- "be firm, solid, steadfast", with derivatives referring to wood. In Indic it became droṇa "wooden trough", then Bengali ডিঙ্গি ḍiṅgi "small boat". This was borrowed into English as dinghy "a small boat or skiff". The sound change seems to be something like droṇa - ḍoṇa - ḍoṅga - ḍiṅgi.
*deru- in the form *drū- became Greek δρῦς drus "tree", then Δρυάς, Δρυάδος Druas, Druados "wood-nymph", then dryad.