The word 'wedlock' originates from Old English wedlāc, a compound of wedd (pledge) and lāc (an action, state, or offering). Literally, it meant "the state or action of pledging." The term specifically referred to the marriage vow or covenant. Over time, the second element -lāc lost its productivity and became opaque, fossilized within this word. Consequently, 'wedlock' evolved from its literal sense of "pledge-state" to denote the abstract, formal institution of marriage itself, often used in legal or formal contexts.

Structure: wed (to marry) + lock (a state or bond) - wed: From Old English weddian meaning "to pledge, covenant, marry." It is a Germanic root. - lock: From Old English lāc meaning "an action, a state, a gift." It is a Germanic suffix forming nouns of action or state.