Druidry

A druid (Welsh: derwydd; Old Irish: druí) was a member of the high-ranking professional class in ancient Celtic cultures. While 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.

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 (50s BCE). Later Greco-Roman writers also described the Druids, including 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 "Táin Bó Cúailnge", 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 are based on the misconceptions of 18th century scholars. These have been largely superseded by more recent study.

...
Wikipedia