In English law, baron and feme is a phrase used for husband and wife, in relation to each other, who were accounted as one person by coverture.
In heraldry, baron and femme are terms denoting the two-halves of an heraldic escutcheon used when the coat of arms of a man and the paternal arms of his wife are impaled (or anciently dimidiated), that is borne per pale within the same escutcheon.
The resultant shield is used by the husband, as in general females are not entitled to display heraldry, unless suo jure peeresses.
Later, in Western Europe, the word was used to refer to a ruler's leading henchmen (e.g. a baron was the King's Man).
Later, it came to have a specific, legal definition as the tenant-in-chief of the early Norman kings, which class developed into feudal barons who held their lands from the king by the feudal tenure per baroniam and were entitled to attend parliament.