Scotia is a Latin placename derived from Scoti, a Latin name for the Gaels, first attested in the late 3rd century. The Romans referred to Ireland as "Scotia" around 500 A.D. From the 9th century on, its meaning gradually shifted, so that it came to mean only the part of Britain lying north of the Firth of Forth: the Kingdom of Scotland. By the later Middle Ages it had become the fixed Latin term for what in English is called Scotland.

The name of Scotland is derived from the Latin Scotia. The word Scoti (or Scotti) was first used by the Romans. It is found in Latin texts from the 4th century describing an Irish group that raided Roman Britain. It came to be applied to all Gaels. It is not believed that any Gaelic groups called themselves Scoti in ancient times, except when writing in Latin. Old Irish documents use the term Scot (plural Scuit) going back as far as the 9th century; for example, in the glossary of Cormac mac Cuilennáin.

Oman derived it from Scuit (modern Gaelic scoith), meaning someone cut off. He believed it referred to bands of outcast Gaelic raiders, suggesting that the Scots were to the Gaels what the Vikings were to the Norse.

The 19th-century author Aonghas MacCoinnich of Glasgow proposed that Scoti was derived from a Gaelic ethnonym (proposed by MacCoinnich) Sgaothaich from sgaoth "swarm", plus the derivational suffix -ach (plural -aich). However, this proposal to date has not been met with any response in mainstream place-name studies. Pope Leo X (1513–1521) decreed that the use of the name Scotia be confined to referring to land that is now Scotland.

Virtually all names for Scotland are based on the Scotia root (cf. Dutch Schotland, French Écosse, Czech Skotsko, Zulu IsiKotilandi, Māori Koterana, Hakka Sû-kak-làn, Quechua Iskusya, Turkish İskoçya etc.), either directly or via intermediate languages. The only exceptions are the Celtic languages, where the names are based on the Alba root; e.g., Manx Nalbin, Welsh Yr Alban", Irish "Albain."

Scotia translates to "Land of the Scots". It was a way of saying "Land of the Gaels" (compare Angli and Anglia; Franci and Francia; Romani and Romania; etc). It was initially used as a name for Ireland, originally with ethnic connotations, for example in Adomnán's Life of Columba, or by Isidore of Seville, who wrote in 580 CE that "Scotia and Hibernia are the same country" (Isidore, lib. xii. c. 6). This is how it was used, for instance, by King Robert I of Scotland (Robert the Bruce) and Domhnall Ua Néill during the Scottish Wars of Independence, when Ireland was called Scotia Maior (greater Scotia) and Scotland Scotia Minor (lesser Scotia).

After the 11th century, Scotia was used mostly for the kingdom of Alba, or Scotland, and in this way became the fixed designation. As a translation of Alba, Scotia could mean both the whole kingdom belonging to the King of Scots, or just Scotland north of the Forth.

Pope Leo X of the Roman Catholic Church eventually granted Scotland exclusive right over the word, and this led to Anglo-Scottish takeovers of continental Gaelic monasteries (e.g., the Schottenklöster).