Druid
A druid (Gaulish: druides, from Proto-Celtic *druwides, 'oak-knower' or '[priest with] strong insight') was a member of the learned class of the ancient Celtic peoples of Gaul and Britain, described by Greek and Roman writers as a priest, teacher, judge and custodian of religious and legal tradition. Because the druids committed nothing of their teaching to writing and cannot be securely identified in the archaeological record, almost everything known about them comes from outside observers.