clot n.

c. 1300, clete "a wedge," from Old English *cleat "a lump," from West Germanic *klaut "firm lump" (source also of Middle Low German klot, klute, Middle Dutch cloot, Dutch kloot, Old High German kloz, German kloß "clod, dumpling").

In Middle English, a wedge of wood bolted to a spar, etc., to keep it from slipping (late 14c.). Meaning "thin metal plate fastened under a shoe, etc." (originally to preserve the sole) is from c. 1825, originally a dialect word. The athletic cleat, for gripping, is attested from 1904.

"lump of earth or clay," Old English clod- (in clodhamer "the fieldfare," a kind of thrush), from Proto-Germanic *kludda-, from PIE *gleu- (see clay).

Synonymous with collateral clot until the meanings differentiated 18c. Meaning "person" ("mere lump of earth") is from 1590s; that of "blockhead, dolt, stupid fellow" is from c. 1600 (compare clodpate, clodpoll, etc. in the same sense). It also was a verb in Middle English, meaning both "to coagulate, form into clods" and "to break up clods after plowing."