In far antiquity the Fir Bolg were the rulers of Ireland (at the time called Ériu) immediately before the arrival of the Tuatha Dé Danann, who many interpret as the Gaelic gods. The King of the Tuatha Dé Danann, Nuada, sued for half the island for his people, but the Fir Bolg king refused. At the ensuing Battle of Mag Tuired (Moytura) the Fir Bolg were all but conquered and their king slain by the goddess Morrigu, though the fierce efforts of their champion Sreng saved them from utter loss, and the Tuatha Dé Danann were so touched by their nobility and spirit they gave them one quarter of the island as their own. They chose Connacht and are mentioned very little after this in the myths.
The origin of their name is the subject of some dispute. Many commentators consider them the "men of Builg" or "men of bags", or by comparison with the modern Irish word bolg meaning 'belly' (and originally meaning 'bag'). Alternatively they may be related to the Belgae tribe, whose name meant the "shining ones" (from Proto-Celtic *belo, meaning "bright"). In Early Irish, "boillsg" meant gleam; from Proto-Celtic *bolg-s-cio-; related to Latin "fulgeo", shine, English "effulgent", Lithuanian "blizgù" and even Russian "byela" (white).
Tribal origins and history
These people arrived in Ireland in three groups, the Fir Bolg, the Fir Domnann and the Gaileanga. According to the model proposed by O'Rahilly, the Fir Bolg are linked to the historical Belgae, known from Gaul and Britain, and to the historical Builg of Munster; the Fir Domnann to the British Dumnonii and the Gaileanga are the Laigin, who founded Leinster. According to this model, the three groups probably represent the Ivernic-speaking peoples who inhabited Ireland before the Goidelic-speaking Gaels.
Other theories have been advanced about the origin of the Fir Bolg. Some scholars have related the name of a Celtic god with the word Bolg. The Fir Bolg, according to one legend, were involved in carrying bags of earth at one point in their history, hence the "Men of Bags" interpretation. Others speculate that "Bolg" relates to a word for small boats.
One interpretation which has gained ground is drawn from the recorded histories. The Fir Bolg, according to this theory, were largely conquered by the Gaels, and thus, as a lower class in society, would have had different customs befitting a lower social status. In particular, this theory holds that "Fir Bolg" is a corruption of a term for "Breeches-Wearers", reasoning that, as manual labourers, the Fir Bolg would have found it useful to wear trousers rather than the robes and garb of the Gaels. This theory, however, remains largely speculative, and there is little hard evidence to confirm this interpretation.
The Fir Bolg were recorded as being ejected from Ireland and returning under a King named Aengus. The Fir Bolg were given, as a place of settlement, the Aran Islands and surrounding coastland (the largest of these Islands, Inishmore--Árainn--is home to a fortress allegedly related to Aengus and the Fir Bolg, Dún Aengus). This episode of history, in which the Fir Bolg come from what is assumed to be a place near modern Scotland, settle in Ireland, and then go to the Aran Islands, on Ireland's western fringe, has given rise to one interpretation of Fir Bolg origins. A Pictish invasion of Ireland is the proposition in this account, and the Aran Islands were a last refuge for this invading force.
The Fir Bolg: The Accursed Hosts of Anwyn
The Fir Bolg are the dead hosts of Anwyn. They are
spirits doomed to eternally wander Anwyn. Some have preserved their ancient flesh by feeding on the living, others must bind themselves to skeletons from the graves and battlefields of Goria,
in order to once more walk the ground above. In the past this was Anu’s curse on her firstborn race, but those accursed perfected the black art of necromancy and have spread the horror of
living death to any other creatures or folk they deem useful to their war effort. The majority of the Fir Bolg people are these discorporated spirits, enduring the horror of exile in Anwyn
until their chance comes to join a raid on Goria, and they can pass through the gates of hell to assume temporary command of the skeleton of some long dead warrior.
The Fir Bolg cannot help who and what they are—the firstborn race of the Goddess’s children, who because of the ambition of their leader and the malice of Crom were cursed by Anu. This terrible punishment has warped and maddened the Fir Bolg, and their perceptions have been totally altered by interminable centuries in the darkness and pain of Anwyn. They burn with the desire for revenge on Anu and they hate the living. At the centre of their campaign against Goria though is Crom’s great lie. Namely that by providing him with blood sacrifices he will lead them to victory over Anu and dominion over the Land of the Ever Living, where they can finally be at peace.
The majority of Anwyn’s hosts reside in that dark, otherworld realm where they have been banished to by the Sidhe and other races of the living. However, there remain parts of Goria, near the major gateways into Anwyn, that the living have never managed to rid of the Fir Bolg threat. Saiber Frith, Mag Slecht, the Mounds of the Old Kings, and Kluruch’s Marsh are but some of the places where the dead haunt the land, and the Fir Bolg hosts can emerge from Anwyn to raid.
When the Fir Bolg march to war they are a terrible and awesome sight. They rely on overwhelming numbers to destroy their enemies and the rank and file of the Fir Bolg have no fear of destruction—skeletons are only temporary carriages, whilst zombies are simply dead flesh to which sundry spiritual fragments have temporarily been bound. They are relentless in battle, and even though the average living warrior is physically more than a match for a skeleton or zombie, living warriors know fear and panic. Perhaps even more terrifyingly, Fir Bolg priests and heroes can raise the dead from the battlefield, including the dead of previous conflicts that may be mouldering in the soil below. Even when the victory looks assured for the living, the Fir Bolg can bring more forces to bear in this way