Druidic

[droo-id] /ˈdru ɪd/

noun, (often lowercase)
1.
a member of a pre-Christian religious order among the ancient Celts of Gaul, Britain, and Ireland.
/ˈdruːɪd/
noun (sometimes capital)
1.
a member of an ancient order of priests in Gaul, Britain, and Ireland in the pre-Christian era
2.
a member of any of several modern movements attempting to revive druidism
adj.

1773, from Druid + -ic. Related: Druidical.
n.

1560s, from French druide, from Latin druidae (plural), from Gaulish Druides, from Old Celtic *derwijes, probably representing Old Celtic derwos “true” and *dru- “tree” (especially oak) + *wid- “to know” (cf. vision). Hence, literally, perhaps, “they who know the oak” (perhaps in allusion to divination from mistletoe). Anglo-Saxon, too, used identical words to mean “tree” and “truth” (treow).

The English form comes via Latin, not immediately from Celtic. The Old Irish form was drui (dative and accusative druid; plural druad); Modern Irish and Gaelic draoi, genitive druadh “magician, sorcerer.” Not to be confused with United Ancient Order of Druids, secret benefit society founded in London 1781.