“                              Knocking on Wood
Indo-European, Celtic, or possibly British

Any list of superstitions would have to begin with arguably the most well-known and universal superstition: ‘to knock on wood.’

The actual origins, and even meanings, of the phrase are as varied as the cultures which use it, with some suggesting roots in the Indo-European or Celtic belief that spirits good and bad resided in trees who could be either called upon for protection or chased away by knocking on their home, and others (particularly Christians) linking the practice to the magical power of the wooden Crucifix.

 Most likely among the different theories, historians have attributed the superstition to a 19th-century British children’s game called “Tiggy Touchwood” in which young players claimed immunity from being tagged by touching the nearest piece of wood. Adults picked up on the habit and the phrase (the British still say “touch wood” today), and the rest is history.

               Throwing Salt Over Your Shoulder
European/Christian, ancient Roman

Perhaps the next most common superstition, at least in the West, involves tossing salt over one’s shoulder. Like ‘knocking on wood,’ this superstition also involves the idea of ‘warding off evil’ - in this case, the Devil himself. In Leonardo da Vinci’s The Last Supper, Jesus’ betrayer, Judas Iscariot, is portrayed as having accidentally spilled salt. Since Judas was associated with doing something bad, the argument goes that, ipso facto, so was salt, and throwing it over your shoulder would blind the devil waiting there. 

Since, in other versions of the superstition, “Old Scratch” was thought to reside just over your left shoulder, ready to tempt you, the salt was thrown to the left.

Still, others say that the sheer value of salt alone in ancient times led to the belief that to spill it was to incur bad fortune (like among Romans), requiring a corresponding ritual or act of penance to prevent worse loss from occurring.

                 Walking Under a Ladder
European/Christian, possibly Egyptian

The superstition of not wanting to walk under a ladder also has roots in Christian symbolism: the “Holy Trinity” of the Father, the Son, and the Holy Spirit led to an association of the number three with something sacred. The triangle, with its three sides, came to be regarded as sacred as well, and a ladder of course forms a triangle, so, naturally, to walk under that ladder would be to destroy the sanctity of the Trinity and thus incur punishment.

The ladder’s resemblance to a gallows also didn’t help matters, nor did the fact of the obvious danger of something falling from it.

Finally, the Egyptians apparently thought that one might accidentally spot a god going up or down on a ladder and so avoided it. Must have made building all those tall pyramids difficult.

                              Broken Mirror
Ancient Greek/Roman, European, etc.

The belief that a broken mirror brings bad luck most likely has its origins in the simple fact that reflections of ourselves are uncanny and often unnerving (particularly on a “bad hair” day), so humans have long had bad associations with them. Take, for example, the Greek myth of Narcissus, or the idea that a crack in a mirror would somehow break its charm or trap one’s soul.