Scoti or Scotti was the generic name used by Late Roman authors to describe the Irish warbands who raided Roman Britain. The earliest instance of the term is in the appendix to the Laterculus Veronensis, dated to c.314. Formerly, Latin writers called the Irish Hiberni. Thereafter, periodic raids by Scoti are reported by several later fourth-/early fifth-century Latin writers, namely Pacatus, Ammianus Marcellinus, Claudian and the Chronica Gallica of 452. Two references to Scoti have recently been identified in Greek literature (as Σκόττοι), in the works of Epiphanius, Bishop of Salamis, writing in the 370s. The fragmentary evidence suggests an intensification of Irish raiding from the early 360s, culminating in the so-called "barbarian conspiracy" of 367-8, and continuing up to and beyond the end of Roman rule c.410. The location and frequency of attacks by Scoti remain unclear, as do the origin and identity of the Irish population-groups who participated in these raids. The term Scoti gradually came to embrace all Gaels. In the fifth century, the Gaelic kingdom of Dál Riata emerged on the west coast of Scotland. As this kingdom grew in size and influence, the name was applied to all its subjects – hence the modern terms Scot, Scottish and Scotland.
The etymology of Late Latin Scoti is unclear. It is not a Latin derivation, nor does it correspond to any known Goidelic term the Irish used to name themselves as a whole or a constituent population-group. The implication is that this Late Latin word rendered a Primitive Irish term for a social grouping, occupation or activity, and only later became an ethnonym. Several derivations have been conjectured but none has gained general acceptance in mainstream scholarship. In the nineteenth century Aonghas MacCoinnich proposed that Scoti came from Gaelic Sgaothaich, meaning "crowd". Charles Oman favoured Gaelic Scuit, with the sense of a "man cut-off" or "broken man", suggesting this was not a general word for Gaels but a band of outcast raiders. More recently, Freeman has speculated on the likelihood of a group of raiders adopting a name from an Indo-European root, *skot, citing the parallel in Greek skotos (σκότος), meaning "darkness, gloom".