Ethnology

The thirteenth entry is regra de casamento, and the English words waiting for it carry a history worth having. « Marriage » came in from French and is the ordinary word, but « wedding » belongs to the older layer and was not about a ceremony at all. In Old English, wedd was a pledge, a security handed over to guarantee a promise, and weddian meant to give such a pledge. What the verb described was the binding undertaking, not the feast. That sense has not quite gone: « to pledge » is still the plain verb for binding oneself, and a person can be « wedded to a method », held to it as if by a promise. « Wedlock » keeps the old noun too, and its second half is not « lock » but the Old English ending -lāc, which built nouns of action and shut nobody in. So for a rule saying who may marry whom, « marriage rule » is the term to use; and « wedding » is best kept for the day itself, with the old pledge still sitting inside it.