"In eighteenth-century London, when metal-spoked waterproof umbrellas began to become a common rainy-day sight, their stiff, clumsy spring mechanism made them veritable hazards to open indoors. A rigidly spoked umbrella, opening suddenly in a small room, could seriously injure an adult or a child, or shatter a frangible object. Even a minor accident could provoke unpleasant words or a minor quarrel, themselves strokes of bad luck in a family or among friends. Thus, the superstition arose as a deterrent to opening an umbrella indoors."
"It's bad luck to walk under a leaning ladder."
This superstition really does originate 5,000 years ago in ancient Egypt. A ladder leaning against a wall forms a triangle, and Egyptians regarded this shape as sacred (as exhibited, for example, by their pyramids). To them, triangles represented the trinity of the gods, and to pass through a triangle was to desecrate them.
This belief wended its way up through the ages. "Centuries later, followers of Jesus Christ usurped the superstition, interpreting it in light of Christ's death," Panati explained. "Because a ladder had rested against the crucifix, it became a symbol of wickedness, betrayal, and death. Walking under a ladder courted misfortune."
In England in the 1600s, criminals were forced to walk under a ladder on their way to the gallows.
"A broken mirror gives you seven years of bad luck."
In ancient Greece, it was common for people to consult "mirror seers," who told their fortunes by analyzing their reflections. As the historian Milton Goldsmith explained in his book "Signs, Omens and Superstitions" (1918), "divination was performed by means of water and a looking glass. This was called catoptromancy. The mirror was dipped into the water and a sick person was asked to look into the glass. If his image appeared distorted, he was likely to die; if clear, he would live."
In the first century A.D., the Romans added a caveat to the superstition. At that time, it was believed that peoples' health changed in seven year cycles . A distorted image resulting from a broken mirror therefore meant seven years of ill-health and misfortune, rather than outright death.
"When you spill salt, toss some over your left shoulder to avoid bad luck."
Spilling salt has been considered unlucky for thousands of years. Around 3,500 B.C., the ancient Sumerians first took to nullifying the bad luck of spilled salt by throwing a pinch of it over their left shoulders. This ritual spread to the Egyptians, the Assyrians and later, the Greeks.
The superstition ultimately reflects how much people prized (and still prize) salt as a seasoning for food. The etymology of the word "salary" shows how highly we value it. According to Panati: "The Roman writer Petronius, in the Satyricon, originated 'not worth his salt' as opprobrium for Roman soldiers, who were given special allowances for salt rations, called salarium 'salt money' the origin of our word 'salary.'"