Meaning

noun a coupler shaped like the letter U with holes through each end so a bolt or pin can pass through the holes to complete the coupling; used to attach a drawbar to a plow or wagon or trailer etc.

originFirst attested in the 1590s. Ultimately related to cleave. Exact origin unknown; probably derived from the verb cleave. If so, the word ultimately may stem from Scandinavian: compare Old Norse kljúfa (“to split”), Old Norse klofi (“a forked stick”).

Etymology from Wiktionary, CC BY-SA 3.0