If leaving your umbrella open to dry in the corner of your office makes you slightly uneasy, you’re probably not alone. When it comes to alleged harbingers of bad luck, open indoor umbrellas are right up there with broken mirrors and black cats. While the origin of the superstition isn’t exactly proven, there are a few leading theories about how and why it began.

One of them suggests it started around 1200 BCE, when the ancient Egyptian priests and royalty were using umbrellas made of peacock feathers and papyrus to shield them from the sun. According to Reader’s Digest, the superstition might have stemmed from a belief that opening an umbrella indoors—away from the sun’s rays—would anger the sun god, Ra, and generate negative consequences.

Another theory involves a different ancient Egyptian deity: Nut, goddess of the sky. As HowStuffWorks reports, these early umbrellas were crafted to mirror (and honor) the way she protected the Earth, so their shade was considered sacred. If anybody with non-noble blood used one, that person supposedly became a walking, talking beacon of bad luck.

The reason we try to abstain from opening umbrellas indoors today, however, is probably more about avoiding injury than divine wrath. Modern umbrellas gained popularity during the Victorian era with Samuel Fox’s invention of the steel-ribbed Paragon frame, which included a spring mechanism that allowed it to expand quickly—and dangerously.

“A rigidly spoked umbrella, opening suddenly in a small room, could seriously injure an adult or child, or shatter a frangible object,” Charles Panati writes in his book Panati’s Extraordinary Origins of Everyday Things. “Thus, the superstition arose as a deterrent to opening umbrellas indoors.”

All things considered, even if opening an umbrella indoors doesn’t necessarily make for bad luck, getting poked in the eye by one can certainly make for a bad day.

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