According to Oxford Languages the literal definition of Celtic is is relating to the Celts or their languages, which constitute a branch of the Indo-European family and include Irish, Scottish Gaelic, Welsh, Breton, Manx, Cornish, and several extinct pre-Roman languages such as Gaulish. The term “Celtic” is used to refer to persons who trace their ancestry back to one of the present Celtic territories located in the westernmost parts of Europe.