The 10th-century Book of Deer contains the oldest known Gaelic text from Scotland, from the Gospel of Matthew.

Middle Irish is the name given by historical philologists to the form of the Irish language from the 10th to 16th centuries; it is therefore a contemporary of Middle English. The modern Goidelic languages Irish, Scottish Gaelic, and Manx are all descendants of Middle Irish. At its height, Middle Irish was spoken throughout Ireland and Scotland; from Munster to the North Sea island of Inchcolm. Almost all survives from Ireland, and little from Scotland or Man. But a form of Middle Irish, known as 'Classical Gaelic', was used as a literary language in Ireland until the 17th century and in Scotland until the 18th century. Inchcolm (Scottish Gaelic: Innis Choluim - Island of Columba) is an island in the Firth of Forth, east of the Forth Bridge, south of Aberdour, Fife, and north of the City of Edinburgh in Scotland. The main feature of the island is the former Augustinian Inchcolm Abbey, Scotland's most complete surviving example of a monastic house.

Situated in the famous Boyne Valley, bordered by Irish Sea and counties Cavan, Fingal, Kildare, Louth, Monaghan, Offaly and Westmeath. An old stone bridge crosses the River Kells, separating Kells from the adjacent village of Connor, near Ballymena in Co. Antrim. There was no monastic establishment at Connor in the Middle Ages, though there was an Augustinian community at Kells nearby. The Synod of Kells completed the transition of the Roman Catholic Church of Ireland from a monastic church to the diocesan church that continues today. Saint Columba and the Abbey Kells, the Book of Kells was produced by Celtic monks around 800 AD at the time of the Viking invasions, by monks from the monastery at Iona off the Western coast of Scotland and as far as Iceland.

According to tradition St. Finian established a church in Achonry (Irish Achadh Chonaire, the field of Conaire), Co. Sligo, in the sixth century and placed his pupil NATHY who was born in the Connemara country of Sligo possibly of the O’Hara family , in charge of it. The boundaries of the diocese emerged in the early twelfth century and it was formally established by the Synod of Kells in 1152 when the present Irish diocesan structure was laid out. Abbot Nathy of Fobhar is commonly referred to in the writings as Crumther Nathy or Cromnathy (Irish Cruimhthir, a priest) in Westmeath, and served as its first abbot. The Irish monks spread Christianity into Cornwall, Wales, and Scotland. Saint Ninian established a monastery at Whithorn in Scotland about 400 AD, and he was followed by Saint Columba (Iona), and St. Aidan, who founded a monastery at Lindisfarne in Northumbria. In 650, Aileran became rector of Clonard, and was recognized as a classical scholar and a master of Latin and Greek. He wrote The Fourth Life of St. Patrick, a Latin-Irish Litany and The Lives of St. Brigid and St. Fechin of Fore. Aileran died from the Yellow Plague. His death on December 29, 664 is chronicled in the Annals of Ulster.

CHAPTER XXXIV ETHELFRID, KING OF THE NORTHUMBRIANS, HAVING VANQUISHED THE NATIONS OF THE SCOTS, EXPELS THEM FROM THE TERRITORIES OF THE ENGLlSH. [A.D. 603.]

AT this time, Ethelfrid, a most worthy king, and ambitious of glory, governed the kingdom of the Northumbrians, and ravaged the Britons more than all the great men of the English, insomuch that he might be compared to Saul, once king of the Israelites, excepting only this, that he was ignorant of the true religion. For he conquered more territories from the Britons, either making them tributary, or driving the inhabitants clean out, and planting English in their places, than any other king or tribune. To him might justly be applied the saying of the patriarch blessing his son in the person of Saul, "Benjamin shall ravin as a wolf; in the morning he shall devour the prey, and at night he shall divide the spoil." Hereupon, Ædan, king of the Scots that inhabit Britain, being concerned at his success, came against him with an immense and mighty army; but was beaten by an inferior force, and put to flight; for almost all his army was slain at a famous place, called Degsastan, that is, Degsastone. In which battle also Theodbaid, brother to Ethelfrid, was killed, with almost all the forces he commanded. This war Etheifrid put an end to in the yeare 603 after the incarnation of our Lord, the eleventh of his own reign, which lasted twenty-four years, and the first yeare of the reign of Phocas, who the governed the Roman empire. From that time, no king the Scots durst come into Britain to make war on the English to this day.

In 1152 (Synod of Kells) Cloyne was made one of Cashel's twelve suffragan sees. From 1265 to 1429 the bishops of Cloyne were mostly Englishmen. In former times, and perhaps partly due to its dedication to Columba, it was sometimes nicknamed 'Iona of the East'. Near Neufchatel en Bray is the village of Mortemer from whence come the Scottish Mortimers. Ralph de Mortemer followed the Conqueror in 1066, and his descendant came to Scotland in the reign of David I. Mortimer's Deep in the Firth of Forth opposite Edinburgh is named after Alan de Mortemer who gifted lands in Fife to the island monastery of Incholm Abbey.

Inchcolm Abbey is a medieval abbey located on the island of Inchcolm in the Firth of Forth in Scotland. The Abbey was first used as a priory by Augustinian monks, becoming a full abbey in 1235. The island was attacked by the English from 1296 onwards, and the Abbey was abandoned after the Scottish Reformation in 1560 during the Treaty of Berwick, which would expel the French from Scotland, is signed by England and the Congregation of Scotland. After the French withdrawl from Scotland, the Treaty of Edinburgh between England, France and Scotland and largely ends the "Auld Alliance" between France and Scotland, and ends the wars between England and its northern neighbour. Then the Roman Church is overthrown and Protestantism was established as the national religion in Scotland.

The Scottish Gaelic name of of the Book of Deer