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Knock on wood: 7 common superstitions and the quirky explanations behind them

Turns out there may be a remedy to bad luck for breaking a mirror

A person stands in front of a broken mirror. (Photo by SHVETS production from Pexels.)

Have you ever paused in your tracks when a black cat crossed your path, or thrown salt over your shoulder after spilling it?

There's a long list of superstitions many of us follow, but why? It turns out there are explanations.

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Breaking a mirror

In case it’s not enough that breaking a mirror may bring bad luck, that bad luck is said to then persist for seven whole years.

A long, long time ago (think ancient Egyptians, Romans and Greeks), mirrors were valuable, and (of course) possessed some mystical attributes, according to the Psychic Library.

In Roman times, it was believed that each person’s body would undergo physical regeneration every seven years. Because a mirror reflected the soul, when one was broken, it signified a break in the person’s health and well-being.

There is good news, though. It is said that if you bury the broken pieces of a mirror underground and under the moonlight, you can avoid the bad luck.


Black cats crossing your path

You may be surprised to know that black cats are actually thought to bring good luck in England, Ireland and ancient Egypt — so much so that the cats were well-protected from death and injury.

But that doesn’t answer the question of why we believe black cats bring bad luck.

Other parts of Europe, during the Middle Ages, thought of cats as companions of witches, or even witches in disguise. When a black cat would cross your path, it meant the devil was watching you. Apparently, the Pilgrims brought the notion to America, and the association between witches and black cats continues to this day.


The number 13

This superstition is so legit that the term triskaidekaphobia was coined for those who have a fear of the number 13.

In short, History.com says Western cultures have long associated the number 12 with good and completeness — think 12 days of Christmas, 12 months, 12 zodiac signs, 12 tribes of Israel and 12 labors of Hercules, to name a few. It has often, in ancient world, been considered a perfect number. So its successor 13 has gotten a bad rap as a sign of bad luck.

To build on that, there are two events that play into the theory that 13 is an unlucky number. Each of those revolve around a 13th guest at ancient events: Judas (who betrayed Jesus) at the Last Supper, and Loki (a Norse god known for being mischievous) at a dinner party in which there was already a perfect balance of 12 gods in attendance.


Walking under a ladder

​As one of the more commonly-known superstitions, there seems to be various theories on where this one came from.

In medieval times, ladders were often associated with gallows, which is where people faced death by hanging. If someone walked under a ladder, it was believed that person would eventually face their death by hanging.

A different theory is that, because people were hung at the top of rungs of the ladder, their spirit would reside in the triangle the ladder created as it leaned against the gallows. By walking under it, some assumed a dead body could fall on them, causing injury or death.

And yet another theory suggests that the triangle created by leaning a ladder up against a wall signified the Holy Trinity -- the spirit of the Father, the Son and the Holy Ghost. Because walking under it was considered a desecration of God, it would, in turn, invite the devil in, bringing bad luck.


Spilling salt

This may have started more as bad form than bad luck.

Salt was quite the expensive commodity in ancient times, so wasting it was frowned upon. It’s believed the “bad luck” was brought about as a way to keep people from wasting it.

OK, but what about the whole throwing-it-over-your-left-shoulder business?

Some believe the devil hangs out over the left side of the body, waiting for an opportunity to pounce, so throwing salt over that shoulder puts it right in his face, stopping him from attacking.

For those familiar with the Bible, another origin of the superstition comes from the famous Last Supper painting, which shows Judas (remember, the guy who betrayed Jesus) having knocked over salt, spilling it all over the table.


Knocking on wood

Surely we’ve all knocked on wood to ward off bad luck from something we’ve said, right?

This one may date back to ancient pagan times, when people believed spirits lived in trees, and touching or knocking on the tree would protect them from bad luck. Psychic Library says knocking on the wood was also seen as a thank-you gesture to the gods for bringing blessings and good luck.

In Irish folklore, touching trees was a way of thanking leprechauns for good luck.


God bless a sneeze

So apparently, this wasn’t something that came about for the sake of being polite.

Even though many cultures have believed for thousands of years that sneezes expelled evil spirits, it is said that in the sixth century A.D., a fatal plague was spreading through Italy. After severe chronic sneezing, death often quickly followed. Live Science says the pope urged the healthy to pray for the sick and ordered a light-hearted response, which eventually led to “God bless you” when someone sneezed.

There are dozens of other superstitions people follow, and many theories as to where they originated. Are some of them silly? Maybe. But chances are, they’ll be sticking around for years to come.

This article was initially published in 2018. It has since been updated.