The practice of carrying the bride across the threshold is thought to stem from the various ‘bride capture’ practices prevalent in some parts of Europe prior to the 19th century. The general gist of this practice involves men abducting women from different tribes for the purpose of marriage. In order to keep these women in a marriage they had not consented to, and to prevent them from escaping and returning to their own people, they would subsequently be kept in bondage.

Encyclopedia of Unusual Sex Practices, Brenda Love, 1992