The gallowglass or galloglass (also spelt gallowglas or galloglas) — from Irish: gallóglaigh (plural), gallóglach (singular) — were a class of elite mercenary warriors who principally were members of the Norse-Gaelic clans of Scotland between the mid XIII century and late XVI century. As Scots, they were Gaels and shared a common background and language with the Irish, but as they had intermarried with the X century Norse settlers of western Scotland, the Irish called them Gall Gaeil (“foreign Gaels”).
Large numbers of gallowglass septs settled in Ireland after being dispossessed of their lands in Scotland for choosing the wrong sides in the Wars of Scottish Independence. The first and probably most famous of these were the MacSweeneys (who unlike most were said to be of native Irish ancestry) settled originally by the O’Donnells in west Donegal. These were followed by MacDonnells, MacCabes, and several other groups settled by powerful Irish nobles in different areas. The gallowglass were attractive as a heavy armour-trained aristocratic infantry to be relied on as a strong defence for holding a position. In time there came to be many native Irish gallowglass as the term came to mean a type of warrior rather than an ethnic designation.
They were a significant part of Irish infantry before the advent of gunpowder, and depended upon seasonal service with Irish chieftains. A military leader would often choose a gallowglass to serve as his personal aide and bodyguard because, as a foreigner, the gallowglass would be less subject to local feuds and influences.
The word kern is an anglicisation of the Middle Irish word ceithern or ceithrenn meaning a collection of persons, particularly fighting men. An individual member is a ceithernach. The word may derive from a conjectural proto-Celtic word *keternā, ultimately from an Indo-European root meaning a chain. It was adopted into English as a term for a Gaelic soldier in mediæval Ireland.
The lower position in a two-tiered army structure, lightly-armed and swiftly moving kern infantrymen attended the more skilled and heavily armoured gallowglass on the battlefield. The dart was the kern weapon of choice; javelins, and slings were also used in battle. They made up the overwhelming majority of Gaelic forces in the Middle Ages.