Old Breton dorguid ('prophetic, magical') represent parallel formations. They could reflect an analogical reformation of inherited Proto-Celtic *dru-wid- to *daru-wid- (based on Celtic *daru- 'oak tree'), or alternatively derive from *do-are-wid- ('who sees beyond').

All these forms stem from a Proto-Celtic noun reconstructed as *dru-wid-s (plural *dru-wid-es). The second element is generally derived from the Proto-Indo-European