Druids inhabited north-western Europe around 2000 years ago. The modern English word comes from the Latin ‘druidēs’; this is derived from the Proto-Celtic ‘druwides’ (‘oak-knower’), which itself is rooted in the Proto-Indo-European words ‘deru-‘ (‘oak’) and ‘weid’ (‘to see’).

All surviving evidence of their existence is from external sources - according to lore, their doctrine prevented them from writing knowledge down, and so their oratory history died out with them. The first account of the Druids was written by Julius Caesar in de Bello Gallico.

He was the only writer who potentially could have encountered them for real - he conquered Gaul for the Romans in 1st century BC, then wrote in 54BC: "The Druids are in charge of all religious matters, superin­tending public and private sacrifices, and explaining superstitions.”

His passage in de Bello Gallico describes a well-structured, powerful, and highly respected organisation, lead by “one arch-druid of supreme power”. He also states that Druidism “originated in Britain and was imported into Gaul”; implying evidence of Anglo-Celtic heritage.

He also describes some of their practices: a yearly council meeting at a holy place, where they dealt with grievances; human sacrifice and use of a ‘wicker man’ in which victims were burnt; and states they have the power to ex-communicate those who go against them from society.

Unfortunately Caesar’s accounts have been criticised as inaccurate by modern historians. One such criticism is that Druids, despite being supposedly of such high standing, do not appear even once in his (or his successor Aulus Hirtius’s) retelling of the Gaulish conquests.

There are two broad groups of written accounts regarding Druids: the Roman and Greek, and the Medieval Irish. Whilst the latter are discussing native heritage (and do so extensively) all texts were written centuries after Druids would have ceased to exist, making them unreliable.

However, the word ‘Druid’ does appear in a poem circa 750 AD written by Saint Blathmac, a distinguished Irish monk, who wrote that Jesus was “better than a prophet, more knowledgeable than every druid, a king who was a bishop and a complete sage."

The next surviving mention of Druids in Ireland isn’t until the creation of written law-texts, in the 7th & 8th centuries. These accounts suggested that the importance of Druids had declined to a mere ‘sorcerer’ as the popularity of Christianity, brought over by the Romans, grew.

Druids appear far less often in Welsh medieval literature, and seem to refer to prophets, rather than pagan priests or sorcerers. It is speculated that both the Welsh and the English borrowed the word from Irish medieval lore, creating the Welsh ‘dryw’ and the English ‘dry’.

Two Roman writers - Pliny the Elder and Suetonius - claimed in their accounts that a Roman emperor (Tiberius, or Augustus and Claudius, respectively) had introduced legal measures in the 1st century AD to eradicate Druids and their practices, specifically human sacrifice.

The strongest evidence of Druids in Britain is the independent evolution of the Celtic word ‘druwid’ and, far beyond the Christianisation of the British Isles completed by 7th century, the persistent existence of the offices ‘bard’ and ‘seer’ in Wales up until 13th century.