Conor mac Nessa, the king of the Ulaidh, currently Northern Ireland, more or less, presided over three royal houses at Eamhain Macha – modern day Navan Fort, near Armagh – in the Ulster Cycle of Irish mythology.
In such a society where one individual is paramount, other members of the social group are ranked in relation to that person. In early Iron Age society in Ireland, the hierarchy was most definitely Chieftains & Kings / Nobles, Warriors & Druids / Farmers / Craft-workers, and at the bottom of the heap, slaves.
The bonds holding such a society together depended upon superstition and belief, taboo and powerful social obligations between the differing strata of society and the consequence of breaking those bonds often led to semi-divine retribution.
To maintain this society, virtues such as loyalty and battle prowess, often accompanied by excessive boasting, are exalted and no better place existed for such vauntings than the Red Branch or Craobh Ruadh, one of the three houses within the kingly compound.
Old Irish had two words for “red”: dergh, bright red, the colour of fresh blood, flame or gold; and ruadh, russet, used for the colour of dried blood and for red hair.
The Craobh Ruadh was where the king sat, surrounded by his nobles and warriors while
The Cróeb Derg (modern Irish Craobh Dearg, “bright red branch”) was where severed heads and other trophies of battle were kept.
The third house was called the Téite Brec or “speckled hoard”, where the heroes’ weapons were stored.
Red Branch Chronicles 