(origin: Local) From the parish and lands of Keith, in Banffshire, Scotland. The name Keith is said to be derived from the Gaelic Gaoth, wind, pronounced somewhat similarly to Keith. The old village and kirk are called Arkeith, which may be a corruption of the Gaelic Ard Gaoth, signifying "high wind," which corresponds to its locality, which is peculiarly exposed to gusts of wind. In some old charters, Keith is written Gith, which still more resembles Gaith. I think the name is derived from the Welsh Caeth, a place surrounded, shut up, inclosed, a deep hollow, a strait. The root of the word is the Welsh Cau, to close, to shut up. Concerning this family, the traditional account is, that they came from Germany in the reign of the Emperor Otho, and from the principality of Hesse, from which they were expelled in some revolution. The first person of this family of whom our oldest historians take notice, is Robert De Keith, to whom Malcom II., King of Scotland, gave the barony of Keith, in East Lothian, as a reward for killing Camus, a Danish general, who then invaded Scotland with a numerous army. The battle was fought at Barry, seven miles from Dundee, where an obelisk, called Camus' stone, still preserves the memory of the victory, and it is said the king, dipping his three fingers in the blood of the general, stroked them along the field of the Scotch champion's shield, to whom, besides the landed estate before mentioned, he gave the dignity of Great Marshal of Scotland.

Arthur, William (1857) An Etymological Dictionary of Family and Christian Names. New York: Sheldon, Blakeman. Public Domain.

KEITH. Several parishes and places in Scotland bear this name, which seems to be a Celtic descriptive term ( Caeth) signifying ' confined or narrow.' The place from which the ancient family of Keith, hereditary Earls-Marshal of Scotland from 1010, derive their surname, is in the parish of Humbie, at the south-western extremity of Haddingtonshire. The district is still known as Keith-Marshall, though the estate has long passed away from the family. This is a sufficient origin of both name and familj to satisfy ordinary curiosity, but the inventive genius of Scottish genealogists goes much further.

Lower, Mark A (1860) Patronymica Britannica: a dictionary of the family names of the United Kingdom. London: J.R. Smith. Public Domain.