Go to a wedding, and you won’t have any trouble finding a bridesmaid.

In modern American culture, bridesmaids traditionally wear identical dresses, usually with bright colors and gaudy designs—hardly the styles that they’d choose for themselves.

That’s not important, of course. The important thing is that the bridesmaids all dress in precisely the same way. That got us wondering: Why?

Why do bridesmaids dress alike? The answer is somewhat complicated.

In 2016, several websites published articles linking bridesmaid dresses to Ancient Rome. According to those publications, Roman bridal parties served a sinister purpose: to distract evil spirits.

The bride-to-be would choose 10 friends to serve as witnesses, but also to confuse evil spirits who might be looking to haunt the ceremony. The bride and her bridesmaids would all dress alike so that the evil spirits couldn’t tell them apart.

Over the centuries, we gradually changed the tradition. Today, the bride dresses in all white, but the bridesmaids still dress the same—a holdover from our cultural roots in Ancient Rome.

That makes an interesting bit of trivia, but unfortunately, it’s probably not true.

However, it is, like all good myths, based on some solid facts. Ancient Roman weddings featured witnesses, but these individuals would simply serve as witnesses to the ceremony, as was required by Roman law. Oh, and those witnesses were all men.

The bride would have female attendants who weren’t as essential to the actual ceremony as the witnesses. The attendants would escort the bride to her husband, but they bore no resemblance to the bride, who would have a white woven tunic belted with a “Knot of Hercules,” symbolizing her status.

She’d also have on a veil, which likely inspired the modern bridal veil.

“[The bride] wore a deep yellow veil which may have been meant to act as a good omen, and marked her entry into society as a married woman who was now expected to cover her head in public,” said Dr. Liz Gloyn of the University of London to The Independent.

In any case, any self-respecting evil spirit could easily spot the bride at first glance.

The actual tradition probably dates back to Victorian times.

In 1841, Queen Victoria’s wedding was a spectacle (as is the case with modern Royal weddings). The Court carefully chose the attire for every person involved with the ceremony.

“[Queen Victoria] had 12 bridesmaids, wearing white off the shoulder fashionable 1840 dresses, with full-blown artificial roses decorating their hair behind their right ears,” Lou Taylor, Professor of Dress and Textile History at the University of Brighton, said to The Independent. “They were all the eldest daughters of the highest strata of the peerage. She gave them each a brooch, an eagle (Prince Albert’s crest) of turquoise and pearls.”

Subsequent Royal weddings maintained the tradition of identically dressed bridesmaids, and at some point, the tradition spread to the United States.

Unfortunately, that’s a bit less entertaining than the “angry spirits” myth, but the truth is sometimes lamer than fiction. In any case, it’s something to keep in mind at the next wedding you attend. You’re all mimicking a long-dead Queen, and that’s why you’ve got to climb into that atrocious lime-green dress.