Tribe or group of people speaking Gaelic living in the northeast of what is now Ireland. They began raiding in the 3c and then migrated to Scotland during the 5c. In early texts, references to Scotia or the Scoti are to these people. After migration the kingdom they founded was known as Dalriada, in what are now Argyll and Bute. Later, in the 9c the Scoti and Picts merged, and the former gave their name to the country. After about the 10c Scotia came to refer to Scotland.
Dictionary of Medieval Terms and Phrases. Christopher Coredon with Ann Williams.