Druids, Bards and Filidh in Irish Society*
https://irelandsown.net/druids1.html
“It is the blackest of infamies to conceal the truth of history,” Old Irish proverb
The poets, called either filí, or filean, were also collectively known as aes dana, which translates to men of arts. They were the servants of the Goddess Dana, (Ana-Áine).They moved freely throughout Ireland and were respected everywhere they went.
In Ireland the three groups — Druids, Bards and Filidh — appear to have shared certain duties and activities: thus, the Bards were primarily singers, praise poets and satirists, but the last two responsibilities also fell to the Filidh. Likewise the Druids and the Filidh shared certain duties, notable prophecy, divination and teaching. Both the Filidh and the Druids trained for many years before gaining full proficiency in their crafts. Caesar tells us that the Druids trained for a lengthy 20 years, and insular sources inform us that the Filidh's apprenticeship lasted for 12.
The Druids seem to have been the most politically influential of the three groups of learned men. They had the ear of the rules and their divinatory powers meant that their advice was sought before any important activity was undertaken. They were mediators between kings and the spirit world. They also controlled the kings by means of gessa — divine injunctions or prohibitions with which they bound rulers to keep their powers in check. By the 7th Century AD, however, many Druidic functions in Ireland had been taken over by the Filidh. Moreover, during the medieval period, the Filidh assumed many of the functions carried out by the bards.
What appears to have happened in Christian Ireland is that when the old pagan system began to lose its hold, so the influence of the Druids also gradually disappeared. But the Filidh remained strong, and they took over many of the old Druidic functions, especially the role of prophesying the future. Indeed the Filidh's political power did not finally disintegrate until British rule prevailed in Ireland in the 17th Century.

The Power of Words
A strong theme running though Irish literature is the power engendered by speech, whether praise, poetry, satire or prophecy. The Bards and Filidh had magic in their voices and utterances, and the poets of later medieval Ireland saw themselves as the successors of the Druids and poets of early legends. One such mythic character was Amairgin, who is described in the Mythological Cycle as one of the Gaels or Celts who colonised Ireland in the last series of mythic invasions, after they had deposed the divine race called Tuatha dé Danaan. Amairgin's name means 'Wonderful Mouth,' and he is said to have chanted a poem called the 'Invocation of Ireland,' as he set foot on the land. In the poem, Amairgin extolled the knowledge and wisdom that enabled the Celts to overcome Ireland's previous inhabitants.
Words had the power to wound as well as to bless. There are many descriptions of the physical deformation that could be caused by the lashing tongue of the satirist, whose blight was in many ways as effective a sanction or control as excommunication in medieval Ireland.
The filidh debated whether poetry was at root a thing of spirit, sparked by the Gods, or whether it was a characteristic inherited from one's ancestors. The phrase that I have given as "ancestors" actually refers to one's father and grandfather, but in Irish society women were also known to be poets. Brighid, one of the most popular and powerful of the Celtic Goddesses, was a poet and the patron of filidh. These powerful Irish women have long been ignored, just as many women poets through the ages in many civilizations have been left in obscurity. I believe this was, and continues to be, an injustice to the many inspired women poets of the world. Socially speaking, the highest ranking poets were those whose parents or grandparents had been filidh, but without the spark of imbas, or poetic inspiration, even the best genealogy was not enough.
An interesting feature of the question regarding the "root of poetry" is that the word indicating the origin of poetry (adtuithi, atuidi) may imply "from the north (atúaid)." Mythologically the north is the place in which the Tuatha de Danann learned their druidic and magical arts. In the tale of the Second Battle of Magh Tuired, it is said that they were "in the northern islands of the world, studying occult lore and sorcery, druidic arts and witchcraft and magical skill, until they surpassed the sages of the pagan arts. They studied occult lore and secret knowledge and diabolic arts in four cities: Falias, Gorias, Murias and Findias." 21 Note that all of these cities are in the north, not scattered to the four directions as many occult authors insist.
https://www.madstone.com/Pages/cauldronpoesy.html