1509, from O.Fr. druide, from L. Druidae (pl.), from Gaulish Druides, from O.Celt. *derwijes, representing O.Celt. derwos "true" and *dru- "tree" (especially oak) + *wid- "to know" (cf. vision). Hence, lit., perhaps, "they who know the oak." O.E., too, had the same word for "tree" and "truth" (treow). The Eng. form comes via L., not immediately from Celtic. The O.Ir. form was drui (dat. and acc. druid; pl. druad); Mod.Ir. and Gael. draoi, gen. druadh "magician, sorcerer." Not to be confused with United Ancient Order of Druids, secret benefit society founded in London 1781.