Arthur, William (1857) An Etymological Dictionary of Family and Christian Names. New York: Sheldon, Blakeman. Public Domain.
CLAY
As described in historical dictionaries
An Etymological Dictionary of Family and Christian Names (1857)
(origin: Local) A town of France in Seine. A lake on the isle of Lewis, Scotland. Clee, hills in Wales. Cle, left-handed, a place lying to the left, in relation to another place. Cledh, cloid, and cladd, in the Gaelic, Welsh, and British, signify a ditch, a trench, a wall; cladh, a church-yard; cledd, Welsh, a sword; Gaelic, claiheamb, from which we have Claymore, a large sword. The same word in Welsh and Gaelic that signifies a river is often applied to a sword, from their resemblance in glittering brightness.
Patronymica Britannica (1860)
CLAY. Several localities bear this name, but the surname must sometimes have been adopted from residence in a clayey district. The forms in the H.R. are Cley, Clai, in le Clay, del Clay, and de la Cleje. Le Clayere may be synonymous, although a Cleymanne was, according to the Promptorium Parvulorum, a dauber or plasterer.
Lower, Mark A (1860) Patronymica Britannica: a dictionary of the family names of the United Kingdom. London: J.R. Smith. Public Domain.
Surname type: Location or geographical feature
Origin: English
Region of origin: British Isles
Country of origin: England
Religion of origin: Christian
Language of origin: English