Druid (c-400 - c-50). A druid was a member of the high-ranking professional class in ancient Celtic cultures. Perhaps best remembered as religious leaders, they were also legal authorities, adjudicators, lorekeepers, medical professionals, and political advisors. While the druids are reported to have been literate, they are believed to have been prevented by doctrine from recording their knowledge in written form, thus they left no written accounts of themselves. They are however attested in some detail by their contemporaries from other cultures, such as the Romans and the Greeks. The earliest known references to the druids date to the fourth century BCE and the oldest detailed description comes from Julius Caesar's Commentarii de Bello Gallico. They were also described by later Greco-Roman writers such as Cicero, Tacitus, and Pliny the Elder. Following the Roman invasion of Gaul, the druid orders were suppressed by the Roman government under the 1st century CE emperors Tiberius and Claudius, and had disappeared from the written record by the 2nd century. In about 750 CE the word druid appears in a poem by Blathmac, who wrote about Jesus, saying that he was. better than a prophet, more knowledgeable than every druid, a king who was a bishop and a complete sage. The druids then also appear in some of the medieval tales from Christianized Ireland like the Tain Bo Cuailnge, where they are largely portrayed as sorcerers who opposed the coming of Christianity. In the wake of the Celtic revival during the 18th and 19th centuries, fraternal and neopagan groups were founded based on ideas about the ancient druids, a movement known as Neo-Druidism. Many popular notions about druids, based on misconceptions of 18th century scholars, have been largely superseded by more recent study. The modern English word druid derives from the Latin druides, which was considered by ancient Roman writers to come from the native Celtic Gaulish word for these figures. Other Roman texts also employ the form druidae, while the same term was used by Greek ethnographers as. Although no extant Romano-Celtic inscription is known to contain the form, the word is cognate with the later insular Celtic words, Old Irish drui druid, sorcerer', Old Cornish druw, Middle Welsh dryw seer; wren '. Based on all available forms, the hypothetical proto-Celtic word may then be reconstructed as * dru-wid-s meaning oak-knower. The two elements go back to the Proto-Indo-European roots *deru-and *weid-to see. The sense ofoak-knower or oak-seer is supported by Pliny the Elder, who in his Natural History considered the word to contain the Greek noun drys, oak-tree and the Greek suffix-ides. Both Old Irish drui and Middle Welsh dryw could also refer to the wren, possibly connected with an association of that bird with augury in Irish and Welsh tradition. Sources by ancient and medieval writers provide an idea of the religious duties and social roles involved in being a druid. The Greco-Roman and the vernacular Irish sources agree that the druids played an important part in pagan Celtic society. In his description, Julius Caesar claimed that they were one of the two most important social groups in the region and were responsible for organizing worship and sacrifices, divination, and judicial procedure in Gaulish, British, and Irish societies. He also claimed that they were exempt from military service and from the payment of taxes, and had the power to excommunicate people from religious festivals, making them social outcasts. Two other classical writers, Diodorus Siculus and Strabo, also wrote about the role of druids in Gallic society, claiming that the druids were held in such respect that if they intervened between two armies they could stop the battle. Pomponius Mela was the first author to say that the druids' instruction was secret and took place in caves and forests. Druidic lore consisted of a large number of verses learned by heart, and Caesar remarked that it could take up to twenty years to complete the course of study. What was taught to druid novices anywhere is conjecture: of the druids' oral literature, not one certifiably ancient verse is known to have survived, even in translation. All instruction was communicated orally, but for ordinary purposes, Caesar reports, the Gauls had a written language in which they used Greek characters. In this he probably draws on earlier writers; by the time of Caesar, Gaulish inscriptions had moved from the Greek script to the Latin script.