You have probably done it this week without noticing. Someone mentions a job interview, a hospital appointment, a wedding forecast — and your hand drops to the nearest wooden surface. A table edge. A door frame. The back of a chair. Nobody taught you that.

It arrived the way most British folklore arrives: quietly, at the kitchen table, passed down alongside "bless you", the magpie rhyme and a pinch of salt flung over the shoulder.

These small protective habits are older than our ability to explain them, and the explanations we attach to them are often shakier than we would like. Here is what plausibly lies behind the best known of them — and how to enjoy them without handing them the keys to your life.

Touch Wood: Trees, Crosses and Calling Safe

The most enduring theory is botanical. Long before Christianity reached Britain, trees were treated as living things with power in them: oaks in particular were sacred to druids, and in wider European belief a spirit or god might dwell in a trunk, a grove or a well-side thorn. Touching the tree was a way of asking for its protection, or thanking it for luck already given. That would explain why the gesture is specifically about wood — nobody reaches for a brick.

A second line of thought ties the habit to the Church. Christ was crucified on wood, so touching or knocking on wood could be read as an instinctive reach for the cross. Pilgrims touched relics; ordinary people clutched a wooden crucifix or a rosary bead. The common variant "knock on wood" fits here too, though knocking has also been explained as a way of waking friendly spirits or startling unfriendly ones away.

The third theory is the most mundane and, to many folklorists, the most persuasive: children's games. In chasing games, touching wood made you safe, immune, untouchable. The words "touch wood" as we use them are surprisingly hard to find in print before the nineteenth century, but that may say more about what writers bothered to record than about when the habit began.

Notice how far the ritual has drifted. A veneer-covered desk, a flat-pack bookcase, a wooden spoon: all accepted. The meaning has loosened, but the gesture has held.

Salt, Sneezes and the Devil at Your Left Shoulder

Salt has been precious for most of human history — used to preserve food, to purify, to seal agreements and to bless. Spilling it was waste, and waste invited punishment. The remedy is oddly specific: take a pinch and throw it over your left shoulder. The left side has long carried a bad reputation (the Latin sinister means left), and tradition puts a waiting devil or ill-disposed spirit behind that shoulder. Salt in the eye is your defence.

In Leonardo's The Last Supper, Judas has knocked over a salt cellar — a detail from the painter, not the Gospels, but one that hardened the link between spilt salt and betrayal.

"Bless you" has at least three candidate origins, and no one can prove which came first. One is plague: a sneeze as the first sign of something fatal, and a blessing for someone who might be about to die. Another is the soul, which was thought able to slip out through the nose or mouth and needed protection while the body was caught mid-sneeze. A third is a story attached to Pope Gregory the Great, said to have ordered prayers for sneezers during an outbreak of plague. The popular idea that the heart stops mid-sneeze is folklore rather than medicine.

Regional rhymes survive too: one for a wish, two for a kiss, three for a letter, four for something better.

Magpies, Black Cats and the Trouble With One

The magpie rhyme is one of the most regionally varied pieces of lore in Britain. One for sorrow, two for joy, three for a girl, four for a boy is the version most of us know, but elsewhere three means a funeral or a wedding, and the later lines shift county by county. The remedies are equally local: salute the bird, doff an imaginary hat, greet it properly — "Good morning, Mr Magpie, how's your wife and family?" — or, in sterner accounts, spit and say "Devil, devil, I defy thee." A single magpie seen through a window was thought worse than one met outdoors.

Black cats split the country neatly. In much of England a black cat crossing your path is bad luck; in Scotland, parts of the north and in seafaring families, it is the opposite — a cat kept for luck, particularly by sailors' wives waiting on a safe return.

Ladders, Umbrellas and Crossed Knives: The Household Rules

Many of the rules Britons grew up with concern objects, and most of them have a practical twin lurking underneath.

• Walking under a ladder. The leaning ladder forms a triangle, read as the Trinity, and an open gap against a wall was thought to be a doorway for spirits. It is also, plainly, a good way to be hit by a falling tin of paint.
• Opening an umbrella indoors. A sun-shade opened inside the house was said to insult the sun, or to cast a shadow over the household's luck. And a wet umbrella drips on the carpet.
• Crossed knives at the table. Two blades in a cross shape were said to promise a quarrel. Someone moves them apart before the argument starts.
• Shoes or a loaf on the table. Shoes carried associations with the dead, and an upturned loaf was thought to sink a ship — a serious matter in fishing families. Bread belongs on the board.Photo: Simon Berger / Pexels