The modern Anglicized name ‘Ireland’ derives from the island’s early Celtic name Īweriū, Old Irish Ériu. This name is likely to have meant ‘the fertile land’, and in its original formation is most likely to have expressed the strong associations between the earth, fertility, and the feminine. This fundamental link between the fertility of the land and female fertility is a universal belief that is further expressed in other early names for Ireland which often transmogrified into female personal names. Along with Ériu, Ireland was identified at times with women named Banba and Fótla.

The Greek Ierne and the Latin form Hibernia (Hivernia) appear to relate to the ethnic name for the island’s people, the Ivernioi. These people are historically recognizable as the Érainn, and are first recorded in Ptolemy’s Geography c. ad 150 (II, 1). Ptolemy places them quite clearly as inhabiting the south-west of Ireland. Later genealogies and sagas imply that various peoples belonging to the Érainn ruled over other regions and that they were once particularly powerful. The Corcu Loígde (‘people of the calf goddess’) ruled considerable lands in the south, while the Dál Riata and Dál Fiatach dominated the north-east and parts of western Scotland well into the medieval period. One of the foremost heroic kings in Irish mythology, Conaire Már, was of the Érainn, and his biography describes his seizing the kingship of Tara, only to lose it and die when he broke all the taboos imposed on him at the beginning of his reign. By the time that early Irish genealogies and laws were committed to writing in the 7th century, three races were designated as the free races of Ireland, namely, the Érainn, the Ulaid (Ptolemy’s Uoluntii), and Féni. The latter consisted of peoples who rose to power in the 5th and 6th centuries ad, among them the Éoganachta of Munster and the Connachta in the northern half of Ireland. Latin writers of Late Antiquity from outside Ireland often refer to the inhabitants of Ireland collectively as Scotti (Orosius, I, 2; cf. Isidore, Etymologies, XIV, 6), a term also used of those in western Scotland (Bede, HE I, 1).

The influence of earlier classical observations on Ireland, such as those made by Julius Caesar (Gallic War, V, 13) or Strabo (Geography, IV, 5, 4), continued to be felt into Late Antiquity. According to these descriptions, Ireland was an island in Ocean on the periphery of the habitable world and barely habitable because it was constantly cold (e.g. ‘glacialis Ierne’: Claudian, De IV Consolatu Honorii 33), a belief that was reinforced by the association of the name Hibernia with the Latin adjective hibernus ‘wintry’. Its inhabitants were savages who devoured human flesh and were enormous eaters. Indeed, the root of the ethnonym ‘Gael’, which became the common name for the Irish, is clearly Welsh Gwˆyddyl, meaning ‘wild men, forest people’. Ireland was where the limits of the habitable earth were fixed. This theme of Ireland being at the ends of the earth is echoed by S. Patrick and by S. Columbanus. The latter transformed this apparent disadvantage into the fulfilment of a momentous biblical prophecy: the conversion of the Irish to Christianity heralded the Second Coming, as Christ’s message had now spread to the ends of the earth.

As contacts with Ireland increased in Late Antiquity, and especially as the Irish were active in raiding and settling western Britain, historians of the period provided more accurate and detailed information than their predecessors. Ammianus Marcellinus, writing about the Barbarian Conspiracy of 367–8, names the Irish (Scotti) among the peoples who were attacking Britain, the others being the Picti and the Atacotti—who also may have been Irish (XXVII, 8, 5). In the 5th century, the Christian historian Orosius made more benign comments on Ireland, declaring that although smaller than Britain in extent, it was of greater value because of the favourable nature of its climate and soil (I, 2). The 5th century saw the beginnings of Latin literacy in Ireland, including the gradual dissemination of texts such as Orosius’ History, and the first accounts to emanate from the island itself. The oldest, and most renowned, of these are the Confessio and Epistola of the British Bishop S. Patrick.

S. Patrick provides us with a first-hand account of Ireland, and of the relations between the Irish and their neighbours, particularly along the western coast of Britain. He confirms that raiding for slaves was a common activity on both sides of the Irish Sea. He himself was captured in his father’s villa, and brought to Ireland when he was 16. In his Epistola, he admonishes a British king, Coroticus, for taking some of his converts away as slaves. On the structure of authority in the country, he relates how he gave gifts to kings and judges, and that the sons and daughters of kings travelled with him and became Christian monks and virgins. This was a society in the throes of a significant cultural and religious change, and, as S. Patrick witnesses, this conversion process was neither swift nor easy. It was also a conversion of people on the fringes of the Roman world, a point stressed a few times by the British bishop in his declaration that he was living ‘as an alien among non-Roman peoples, an exile on account of the love of God’ (Epistola, section 1).

In regard to the physical characteristics of the countryside and its economy, the archaeology of Late Antiquity in Ireland is only just beginning to yield a coherent picture. During the first centuries ad, intensive farming seems to have declined and there was a consequent phase of woodland renewal. Settlements are difficult to identify but the methods for disposal of the dead show a shift from cremation to extended inhumation, most particularly from the 5th century onwards. This change does not necessarily reflect the adoption of Christianity, as many graves of the period are not situated in known ecclesiastical sites but rather in ancestral burial mounds (ferta). An occasional burial is accompanied by grave-goods, which must have a religious significance. A spectacular example is that of a woman buried during the 4th/5th century in a prehistoric mound in Fartagh, County Galway, along with the complete body of a horse.

Nevertheless, archaeological evidence for contacts with western Christendom is becoming more evident. Roman material in Ireland is broadly divided into two phases. Objects dating to the 1st/2nd centuries ad are often linked to refugee movements from Britain. A later 4th- to 7th-century phase reflects increasing trade contacts with the Late Roman world. Imports of pottery included containers for wine, olive oil, and other provisions and also high-status tableware. Imports of coins and jewellery, and military payments in the form of hoards of hack silver, support the historical record that the aristocracy in Ireland was well aware of Roman culture and also that it served in the armies of the Late Roman Empire.

Christianity percolated into Ireland in various ways. The papal missions of Popes Celestine and Leo I arrived in the person of Palladius, the courtier sent to Ireland in ad 431 ‘to those Irish believing in Christ’. Christianity came from Britain through missionaries such as S. Patrick, and through personal contacts, most of which were probably familial.

Significant changes happened to Irish society and its economy during the 6th century. Palaeobotanists and ecologists have identified a narrowing of tree rings in Ireland between ad 536 and 541 caused by some natural phenomenon, either volcanic or climatic, in line with similar evidence for the Dust Veil of 536 recorded worldwide. Chronological references are made in the Annals of Ulster (536 and 539) to ‘a failure of bread’ which suggests outbreaks of famine at that time.

A change in settlement patterns, which led to the existence of far more visible monuments in the countryside, came with the building of thousands of ring forts or raths and lake dwellings (crannogs). These were the farmsteads of early Ireland that supported a cattle-based dairying economy and afforded shelter and protection to the free classes. They can be seen dotted throughout Ireland, often with internal mounds surrounded by at least one bank and ditch. Crannogs, small man-made islands built on raft-like foundations and protected with woven wooden palisades, are particularly prevalent in the Midland and northern Lakelands.

The establishment of churches, and most especially monastic communities, contributed to economic and social change. Monasticism appears to have brought industrial mills and milling to Ireland, while such communities also provided for the poor in times of crisis and acted as trade distribution points. Such transformation also caused political upheaval that brought about the downfall of many old dynasties and the rise of new dynasties who were to hold on to power until the 12th century.