Emily Dickinson Lexicon

DRU'ID, n. [Ir. draoi, formerly drui, a magician, a druid; plur. draoithe; Sax. dry, a magician; W. derwyz, {derwyth,} which Owen supposes to be a compound of dar, derw, an oak, and gwyz, knowledge, presence. The Welsh derivation accords with that of Pliny, who supposes the druids were so called, because they frequented or instructed in the forest, or sacrificed under an oak. But some uncertainty rests on this subject.]

A priest or minister of religion, among the ancient Celtic nations in Gaul, Britain and Germany. The druids possessed some knowledge of geometry, natural philosophy, &c., superintended the affairs of religion and morality, and performed the office of judges. – Owen. Encyc.