clot (n.) Look up clot at Dictionary.com
Old English clott "a round mass, lump," akin to Dutch kloot "ball," Danish klods "a block, lump," German Klotz "lump, block;" probably related to cleat and clod.
clot (v.) Look up clot at Dictionary.com
early 15c., from clot (n.). Of fluids from 1590s. Related: Clotted; clotting.