More than meaningless etiquette

Among the Germanic Goths, a man married a woman from within his own community. When women were in short supply, he captured his bride-to-be from a neighboring village. The future bridegroom, accompanied by a male companion, seized any young girl who had strayed from the safety of her parental home. Our custom of a best man is a relic of that two-man, strong-armed tactic; for such an important task, only the best man would do. From this practice of abduction, which literally swept a bride off her feet, also sprang the later symbolic act of carrying the bride over the threshold of her new home.

A best man around A.D. 200 carried more than a ring. Since there remained the real threat of the bride's family attempting to forcibly gain her return, the best man stayed by the groom's side throughout the marriage ceremony, alert and armed. He also might serve as a sentry outside the newlywed's home. Of course, much of this is German folklore, but it is not without written documentation and physical artifacts. For instance, the threat of recapture by the bride's family was perceived as so genuine that beneath the church altars of many early peoples - including the Huns, the Goths, the Visigoths, and the Vandals - lay an arsenal of clubs, knives, and spears.

The tradition that the bride stand to the left of the groom was also more than meaningless etiquette. Among the Northern European barbarians (so named by the Romans), a groom placed his captured bride on his left to protect her, freeing his right hand, the sword hand, against sudden attack.

from Extraordinary Origins of Everyday Things by Charles Panati, 1987