Nomenclature
Although Irish and Manx are often referred to as Irish Gaelic and Manx Gaelic (as they are Goidelic or Gaelic languages), the use of the word Gaelic is unnecessary because the terms Irish and Manx, when referring to language, only ever refer to these languages, whereas Scots has come to refer to a Germanic language, and therefore "Scottish" can refer to things not at all Gaelic. The word Gaelic by itself is sometimes used to refer to Scottish Gaelic and is thus ambiguous.
The names used in the languages themselves (Gaeilge/Gaolainn/Gaelic in Irish, Gaelg/Gailck in Manx, and Gàidhlig in Scottish Gaelic) are derived from Old Irish Goídelc, which comes from Old Welsh Guoidel meaning "pirate, raider".
Read more about this topic: Goidelic Languages