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Brehon (Irish: breitheamh - IPA brᶽehəvɤ or brᶽejuː) is a term for a historical arbitration, mediative and judicial role in Gaelic culture. Brehons were part of the system of Early Irish law, which was also simply called "Brehon law". Brehons were judges, close in importance to the chiefs.
Ireland's indigenous system of law dates from the Iron Age. Known as Brehon law, it developed from customs which had been passed on orally from one generation to the next. Brehon law was administered by brehons. They were similar to judges, though their role was closer to that of arbitrators. Their task was to preserve and interpret the law.
The brehons of ancient Ireland were wise individuals who memorised and applied the laws to settle disputes among members of an extended family. Some brehons were attached to clans, and were allotted a portion of land for their support. Others lived independently by their profession. They were recognised as a professional class apart from druids and bards, and became, by custom, to a large extent hereditary.
In ancient Ireland, Brehons, as part of the leading members of society, would take part in an event which took place every three years on Samhain known as Feis Teamhrach(Festival of Tara) in the House of the Banquet’s(Teach Moidhchuarta) at the Hill of Tara. The assembly was also originally referred to as an Aonach in Pre-historic times. It was a national event with the purpose of resolving any regional disputes regarding title to rank, property and privilege. They would be settled by the lawmakers, the Brehons, and all annals and records would be carefully noted and entered by the Ard Ollams in the official records. The event was founded in very early period and lasted until 560 AD when the last assembly was held by King Dermot, son of Fergus. 
The preparatory course of study extended over some twenty years. The Brehon laws were originally composed in poetic verse to aid memorisation. Brehons were liable for damages if their rulings were incorrect, illegal or unjust. When one brehon had adjudicated on a matter submitted to him, there could be no appeal to another brehon of the same rank; but there might be an appeal to a higher court, provided the appellant gave security. The ranking of a brithem was based on his skill, and on whether he knew all three components of law: traditional law, poetry, and (added later) canon law.
In Prechristian Medieval Ireland prior to the earliest written manuscript. Law was practised by hereditary judges known as bards or fili, who passed on information orally down the generations, they held the positions of Ollam to a provincial High king or rí.
In pre-Norman times, it was the King who passed judgement, when necessary, following recitation of applicable law and advice from the Brehon.
While originating in Oral legal history, it is a common belief that Brehon law enacted the first piece of copyright legislation in relation to written text in world legal history. It involved a bitter dispute around 561 AD between Saint Colmcille and Saint Finian over the authorship of a manuscript called ‘St Jerome’s Psalter‘. Despite the enactment of the law by the king, a bloody conflict still took place known as Battle of Cúl Dreimhne, which resulted in many deaths. 
The ancient law of succession or Tanistry has its origins in Brehons law. It was a Gaelic custom where legally the eldiest son(Tánaiste) succeeded his father to exclusion of all collateral claimants. In terms of land inheritance it was a similar system to Gavelkind in ancient Ireland.
One of the main responsibilities of a Brehon was to record the genealogies of the people. One of the most notable Brehons associated with recording genealogies was the Clan Mac Fhirbhisigh. Dubhaltach Mac Fhirbhisigh produced Leabhar na nGenealach, also the abridgment version Cuimre na nGenealach and Great Book of Lecan. The genealogist would also be referred to in old Irish as a Seanchaidhe. The basic family unit under brehon law in ancient Ireland was defined as Derbfine, or ‘True Kin’ in English
Towards the end of the 13th century, element’s of native Irish Brehon law, through necessity where incorporated into the English common law in the area’s of The Pale, it was referred to as March Law. King Edward I of England, had a need at that particular time to divert much needed resources from Ireland, to concentrate on conflicts elsewhere. As a result English Settlers, especially outside of the Pale began to develop Irish Customs, manner of dress and become accustomed to the native Brehon law. Its popularity amongst what were known as the ‘Old English(Pre-Reformation)’ in Ireland would become a source of concern for future English Monarchs and ultimately accumulated in King Edward III later enforcing the Statutes of Kilkenny in 1366 to counteract its growing popularity among his own subjects in Ireland.
Several dozen families were recognised as hereditary brehon clans.
Maeltine Mor Brethach (The Great Judgement)
Its unknown when the first rudiments of Brehon Law were first practised, some suggest as far back as the Iron age. With it being orally practised, not much documented writings were produced prior to the Christian age. Some information was later passed on and translated or pieced together from the oldest surviving manscripts by the endeavours of Christian Monks, much of it was in the form of myth and poetry.
One of the earliest mythical references to a judgement of a Brehon was following the second Battle of Moytura. The then king of the Tuatha de Danann, Lugh consulted with Maeltine, his Brehon on the capture of Bres, ex-king and a defector to the Formorians. Lugh agreed to spare Bris's life, if he ensured that Irish cows give milk in abundance, by teaching the people of the Tuatha de Danann agriculture.
The second Battle of Moytura was not the first ever documented mythical judgement by Brehon, According to Lebor Gabála the first ever recorded case involved a dispute between Partholón and his adulterious wife, Dealgnaid, a Brehon was said to have adjudicated a settlement between both parties.
Book of Aicill and Fénechus Law
The first ever attempt at transferring Brehon law into written code or legal text was carried out under the patronage of King Cormac mac Airt, he produced the Book of Achall or Aicill, written between 227-266 AD, it relates mainly to criminal law. Cormac is said to have retired to the mound of Aicill, in what is now called Skreen near Tara and started working on the book.
Another later significant document was Senchas Már or Fénechus Law (that which relates to the Féine), drafted around 438 AD by a select committee of nine, presided over by Saint Patrick. Senchas Már is mostly associated with ancient Civil law, selective parts of Pre-Christian Irish Law that were deemed non-compatible to the teachings of the new Christian age were excluded by the committee from the final written tract. Dubthach maccu Lugair was the judge or Brehon chosen by St Patrick, as part of the committee of three kings, three bishops and three professors of literature, Poetry and law, in the creation of Senchas Már.
The earliest tracts were produced in the oldest archaic form of Irish dialect known as 'Bérla Féine’, some also suggest the written text to be an ancient poetic legal dialect of Dubthach.. According to Irish myth the ‘Feine’ were descendants of a legendary figure known as Fénius Farsaid, who is said to have created the ancient language ‘Bérla Féne’. These early manuscripts proved a difficult challenge for centuries after to translate for future academics and even to later Brehon’s. Only in the Seventeenth century Irish Gaelic Scholars such as Eugene O'Curry and John O’Donovan managed to translate much of these original text but only due to a life-long study.
Berla Fene was one of the five extensions of the Goídelc language, it was known as the legal dialect or dark speech of the Filí and the Brehon. The 7th century Manuscript Auraicept na n-Eces or ‘Scholars Primer’, describes the mythical origins of the Ollav, Seventy two named linguistic scholars who had assisted Fenius Farsaid, later asked him to select from all the languages, and develop a tongue that nobody else should have but which might belong to them alone. Fenius created Berla Tobaide and later commanded Gaedheal son of Eathor or Goídel mac Ethéoir to set about arranging and regulate into five dialects and name them all after himself. Berla Fene makes up the Corpus of the earliest written manuscripts and proved the most challenging to translate in the Christian Era.
The Bee Laws
One of the more unusual tracts in Brehon law was known as the Bee Judgment(Bech Bretha). In the twenty page manuscript it goes into great details about legal entitlements or ownership of a swarm(faithche), hives, nests or honey found on a piece of land or property, discovered by a finder or property/land owner and also a detailed compensation scheme for victims of bee stings.
Honey was considered of great value at a time before the advent sugar cane. It had many applications such as basting meat while roasting, treating salmon while broiling, also used as an ingredient in lard and drinks. One of the more important celtic customs was in the production of mead(fermenting of honey with water), in medieval times the alcoholic drink had mystical and religious qualities, an noted example was Lindisfarne Mead, produced by the Celtic Monks on Holy island. The word ‘mither’ derives from the mether, which is a mead drinking vessel. People are said to get ‘confused and bothered as a result of too much mead’.
Mead is also associated with the wife of Ailill and Sovereignty Queen, Medb. In Pagan times, Brehon law states that before a new High King can be inaugurated they must first accept an alcoholic drink in form of Mead off the Queen of the Land, and thus become intoxicated by her.
Brigh Brigaid, also spelled as Briugaid or Brughaidh, (flourished circa CE 50, Ireland) was a woman who held office as a brehon, or judge, in Ireland in the 1st century CE. Brigh is mentioned in the Senchus Mór, a compendium of the ancient laws of Ireland, and her decisions were cited as precedents for centuries after her death.. Her name is possibly associated to the Celtic Pagan Goddesses, who had a strong connection with the bardic traditions. She was known as the “great brig” or brigit, an honored brehon women who is said to have healed a fellow judge, Sencha mac Ailella blotched face by correcting his biased judgement against women.
- Mac Aodhagáin
- Mac Fhirbhisigh
- Ó Cianáin
- Ó Cléirigh
- Ó Cobhthaigh
- Ó Domhnalláin
- Ó Duibh dá Bhoireann
- Ó Breaslain
- Ó Deoradhain
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