There’s something about sunglasses that can make the wearer look like a mega-rock star—think Anna Wintour, Karl Lagerfeld, or actual rock star John Lennon. Conversely, they can also make the wearer instantly detestable—think anyone you’ve personally met who has worn sunglasses inside at night and seemed like a mega-douche.

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This might be because the original point of sunglasses was to hide the wearer’s true feelings. They were first worn in the 12th century by Chinese judges. It's not because they needed protection from the sun; the earliest colored lenses wouldn’t offer much. It’s because they wanted to appear expressionless when they heard cases.

If eyes are the window to the soul, these judges wanted a little shutter to pull down. This makes a ton of sense: Trials go best if a judge appears impartial, and it certainly seems more practical than, say, modern judges in Britain inexplicably still wearing white wigs.

Sunglasses made their way from China to Italy in the 15th century, and by the 18th century, they were thought to be able to improve people’s vision. The glasses were tinted, often green. This actually did sort of work, as green both filters out blue light and offers high contrast between objects, making them easier for people with fading vision to see. They were even marketed to elderly people with the motto, "A blessing to the aged."

While this was useful and excellent and living long enough to need sunglasses was a superb accomplishment back then, this probably isn’t the reason people wearing sunglasses today seem cool. It’s a safe bet that Anna Wintour doesn’t live behind hers because she imagines herself an aged person.

By the 19th century, sunglasses started offering greater protection from the light and were being worn by a much younger population, namely those suffering from syphilis. In part, this was because sensitivity to light is a symptom of the STD. Additionally, it was easy to suspend a metal nose covering between the sunglasses.

You see, this was very helpful since one of the more notable symptoms of syphilis is that it causes noses to rot off. Or, at least, it often leads to saddle nose and skin deterioration around the nostrils. People in the late stages of the disease would often wear contraptions that looked a little bit like those glasses-and-fake-nose accessories you see on Halloween.

Interestingly, the glasses for this use would be about the same shape and tint as the ones John Lennon wore in his heyday and that people constantly wore in the '90s. That’s something later users likely didn't consider when they picked them up. After all, penicillin has been around since the 1920s, so it’s unlikely that anyone would see them and say, "Look! A syphilitic!" I would, though, and now you can, too.

Obviously, the fact that they were used to help treat and disguise the ravages of an STD did not make sunglasses sexy. It’s hard to say that anyone who no longer has a nose on their face is traditionally sexy. It did, however, mean that they were associated with sex and a Victorian notion of sin.

By the 1920s, sunglasses were being worn by silent movie vamps in Hollywood, and therefore still associated with sin. It wasn’t because those stars wanted to protect their eyes against the bright California sun, though. Rather, the early cameras photographing them at premieres and parties had flashbulbs that were filled with magnesium.

The pure, insanely bright white light produced as a result of dozens of them going off at the same time would be literally blinding. And that wasn’t the only problem: The arc lights used in early films were also so bright that starlets were often left with red, watery eyes they didn’t want their fans to see. Basically, being an early movie star caused a ton of eye strain.

This also meant that women across America wanted sunglasses so they could look just like Gloria Swanson. (For as long as there have been movie stars, we’ve wanted to look like movie stars.) While silent screen actors also used sunglasses to help hide their identity when they were out in public, they were a pricey accessory prior to the late '20s, and could actually attract attention rather than divert it.

The first mass-produced sunglasses were made by Foster Grant's Sam Foster in 1929; polarized versions created by Edward H. Land, co-founder of Polaroid, became available in 1936. Aviator glasses made by Ray-Ban became especially sought-after during the 1940s as pilots used them during the war, making them seem more masculine and appealing to male consumers. Housewives likewise used them in the 1950s and 1960s; the cat eye kind Marilyn Monroe wore was initially the most popular, replaced by the oversized ones Jackie Kennedy favored.

Another fun fact is that they were used in mid-century noir films for the exact same reason they’d been used by Chinese judges in the 12th century: Shady dames employed them to hide their true emotions. There’s a scene in Double Indemnity where Phyllis Dietrichson (played by Barbara Stanwyck) wears a pair of sunglasses while browsing a grocery store, one place no one ever needs to wear sunglasses. In this case, they served only to indicate that she had secrets.

Today, people don’t have blindingly bright lights going off in their eyes, but they do still have secrets. We’re willing to permit Karl and Anna that mystery, but when one of our peers dons sunglasses to hide their expression, we’re quick to think they’re just trying to make themselves seem more interesting than they are.

All of which is to say, the next time you see a guy wearing sunglasses in a dark bar, don’t immediately assume he sucks. He could be a time-traveling movie star, or a reputable judge trying to bring back a very practical accessory. Or he could be a douchebag trying to act like a rock star, but you owe it to him to at least ask if he’s suffering the ravages of syphilis first.

Jennifer Wright is the author of It Ended Badly: The 13 Worst Break-Ups in History, due out fall 2015. Follow her on Twitter and Instagram.