druidyoudaoicibaDictYouDict[druid 词源字典]
druid: [16] Druid is, not surprisingly, of Celtic origin, although English probably acquired it via French druide or the Latin plural druides. The source of these forms was Gaulish druides, which came ultimately from Old Celtic *derwíjes. There are two opposing theories on the derivation of this: one is that it comes from an Old Celtic adjective derwos ‘true’ (source of Welsh derw ‘true’), in which case its etymological meaning would be ‘someone who says the truth’ (a parallel formation to English soothsayer); the other is that it was formed from the Old Celtic base *dru- ‘tree’ (source of Welsh derwen and Irish daur ‘oak-tree’ and related to Greek drus ‘oak’ and English tree) in reference to the central role played by oak-trees in druidic ceremonies.
[druid etymology, druid origin, 英语词源]
Druid (n.)youdaoicibaDictYouDict
1560s, from French druide, from Latin druidae (plural), from Gaulish Druides, from Celtic compound *dru-wid-, probably representing Old Celtic *derwos "true"/PIE *dru- "tree" (especially oak; see tree (n.)) + *wid- "to know" (see 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.