Although in the U.S. we believe that having a black cat cross your path is bad luck, it's not the same the world over. In Egypt, for example, all cats are considered lucky. This dates back to ancient times, when cats were considered sacred. Our modern-day fear of black cats may stem from the Middle Ages, when it was believed that a witch could take the form of a black cat
Breaking A Mirror
The belief that you’ll have seven years' bad luck if you break a mirror is said to come from the Romans, who were the first to create glass mirrors. But long ago, many cultures, including Greek, Chinese, African and Indian, believed that a mirror had the power to confiscate part of the user’s soul. The thinking was that if the mirror was broken, then the person's soul would be trapped inside
A LadderAn open ladder forms a triangle, and triangles were once considered a symbol of life, so walking through that shape was considered tempting your fate. It is also thought that because it has three sides, the triangle symbolizes the Holy Trinity, and “breaking” it by entering the triangle is bad luck
The belief of tossing a pinch of salt over your left shoulder to get rid of bad luck come from the legend that the devil is always standing behind you, and throwing salt in his eye distracts him from causing trouble. Nowadays, most people only do this after spilling salt, which is thought to be bad luck because salt was an expensive commodity long ago and folklore linked it to unlucky omens in order to prevent wasteful behavior.
Knocking On Wood
Knocking on wood, or simply saying "knock on wood" after making a hopeful statement, is rooted in the idea that you’re tempting fate by acknowledging your good fortune. The expression comes from the ancient belief that good spirits lived in trees, so by knocking on something wooden, a person was calling on the spirits for protection.
Opening An Umbrella Inside
One explanation for this one comes from the days when umbrellas were used as protection from the sun; opening one inside was an insult to the sun god. Another theory: An umbrella protects you against the storms of life, so opening one in your house insults the guardian spirits of your home, causing them to leave you unprotected
Saying “Bless You”
Considered a polite response to a sneeze, the phrase is attributed to Pope Gregory the Great, who said it to people who sneezed during the bubonic plague. "Blessing" someone after they sneezed originated from the erroneous beliefs that the soul escapes the body during a sneeze and that the heart momentarily stops as well. Therefore, saying “God bless you” was a way of welcoming the person back to life.
This one can be traced as far back as the seventh century B.C., when the rabbit was considered a talismanic symbol, and the left hind foot was a handy way to benefit from the rabbit’s luck. In some cultures, this foot is believed to promote reproduction, so women carry one around to boost their odds of conceiving.
Crossing Your Finges
It’s a near-universal sign of wishing for something, but there are many theories about its origin. One is that when Christianity was illegal, crossing fingers was a secret way for Christians to recognize each other. Another is that during the Hundred Years' War, an archer would cross his fingers to pray for luck, before drawing back his longbow with those same fingers.
Legend says that when Adam and Eve were evicted from the Garden of Eden, Eve snatched a four-leaf clover as a remembrance of her days in Paradise. Since then, lucky attributes have been assigned to all four-leaves of the rare plant—each associated with St. Patrick and the Holy Trinity in Irish legend.
There are several theories here. The first is that the devil appeared at the door of a blacksmith, who agreed to remove a shoe from his hoof if he promised to never enter a place where a horseshoe is hung over the door. The second belief is that witches rode on broomsticks because they were afraid of horses, so a horseshoe is a good charm for scaring them off.
Many people the world over believe that if a bird lets loose on you, then good things are coming your way. One idea is that it's a sign of major wealth coming from heaven, based on the belief that when you suffer an inconvenience (albeit a pretty gross one), you'll have good fortune in return.