One widespread explanation of the belief that it is unlucky to spill salt is that Judas Iscariot spilled the salt at the Last Supper. Leonardo da Vinci's The Last Supper depicts Judas Iscariot having knocked over a salt-cellar.
A more simple explanation is that salt used to be extremely expensive and spilling it was associated with future loss in general. Another explanation may be that salt makes the soil barren for a long time, so spilling salt is a form of cursing a land.
This may not be the actual explanation; salt was a valuable commodity in ancient times, and as such a symbol of trust and friendship. A German proverb held that "whoever spills salt arouses enmity". According to Charles Nodier, among "savages", the "action of spilling salt ... indicates among them the refusal of protection and hospitality from such strangers as they may have reason to suspect are thieves and murderers."
Salt is also a religious symbol. Salt is used to make holy water in the Roman Catholic Church rite, and as such figures as a religious symbol of sanctity, associated with exorcism. The meals served at the witches' sabbath were thought to be salt-free as a consequence. Salt is a symbol of the preserving value of sanctity in Jesus' reference to the "salt of the earth". As an emblem of sanctity and protection, its inadvertent loss may be more than a natural misfortune.
A variety of methods are used to avert the evil omen of spilt salt. The most common contemporary belief requires you to toss a pinch of the spilt salt over your left shoulder, into the face of the Devil who lurks there. A 17th-century report discusses the folk belief that spilling wine is a lucky sign, and mentions a diner who spilt salt and became quite agitated until a waiter had poured wine into his lap.
The belief in the ill luck that comes from spilt salt is quite old, going back to ancient Rome. The 1556 Hieroglyphica of Piero Valeriano Bolzani reports that "(s)alt was formerly a symbol of friendship, because of its lasting quality. For it makes substances more compact and preserves them for a long time: hence it was usually presented to guests before other food, to signify the abiding strength of friendship. Wherefore many consider it ominous to spill salt on the table, and, on the other hand, propitious to spill wine, especially if unmixed with water."
Some have scoffed at the omen. Herbert Spencer wrote that "A consciousness in which there lives the idea that spilling salt will be followed by some evil, obviously allied as it is to the consciousness of the savage, filled with beliefs in omens and charms, gives a home to other beliefs like those of the savage."
- Robert Means Lawrence, "The Folk-lore of Common Salt", in The Magic of the Horseshoe, with Other Folk-lore Notes, s. V
- E. Cobham Brewer, "Salt", in Brewer's Dictionary of Phrase and Fable
- CSICOP, Spilt Salt
- Lawrence, supra
- M. Betham-Edwards, "Charles Nodier", in The Gentleman's Magazine, vol. CCLXII, Jan–June 1878, p. 716
- In the rite for the preparation of holy water, first the salt is exorcised; then the salt is used to exorcise the water. Rituale Romanum, Ordo ad faciendam aquam benedictam (pre-Vatican II rite: Latin language link)
- Lawrence, ss. II
- Lawrence, ss. V, above
- Brewer's Dictionary of Phrase and Fable, above
- Alioqui sal amicitiae symbolum fuit, durationis gratia. Corpora enim solidiora facit et diutissime conservat. Unde hospitibus ante alios cibos apponi solitum, quo amicitiae firmitas ac perseverantia significetur. Quare plerique ominosum habent si sal in mensam profundi contigerit. Contra vero faustum si vinum atque id merum effusum sit. Quoted by Lawrence, ss. 5, supra (and attributed to "Joanne Valeriano").
- Herbert Spencer, The Study of Sociology (Appleton, 1875), ch. 1, "Our Need of It", p. 5.