Owing to the importance of salt as a relish, its Latin name sal came to be used metaphorically as signifying a savory mental morsel, and, in a general sense, wit or sarcasm. It was formerly maintained by some etymologists that this word had a threefold meaning according to its gender. Thus, when masculine, it has the above signification, but when feminine it means the sea, and only when neuter does it stand for common salt. The characterization of Greece as "the salt of nations" is attributed to Livy, and this is probably the origin of the phrase "Attic salt," meaning delicate, refined wit. The phrase cum grano salis may signify the grain of common sense with which one should receive a seemingly exaggerated report. It may also mean moderation, even as salt is used sparingly as a seasoner of food.
Among the ancients, as with ourselves, Sol and sal, the Sun and salt, were known to be two things essential to the maintenance of life.
Soldiers, officials, and working people were paid either wholly or in part in salt, which was in such general use for this purpose that any sum of money paid for labor or service of whatever kind was termed a salarium, or salary, that is, the wherewithal to obtain one's salt.
Pliny remarked that salt was essential for the complete enjoyment of life, and in confirmation of this statement he commented on the fact that the word sales was employed to express the pleasures of the mind, or a keen appreciation of witty effusions, and, therefore, was associated with the idea of good fellowship and mirth.
A certain mystic significance has been attributed to the three letters composing the word "sal." Thus, the letter S, standing alone, represents or suggests two circles united together, the sun and the moon. It typifies, moreover, the union of things divine and mundane, even as salt partakes of the attributes of each. A, alpha, signifies the beginning of all things; while L is emblematic of something celestial and glorious. S and L represent solar and lunar influences respectively, and the trio of letters stand for an essential substance provided by God for the benefit of his people. In a curious treatise on salt, originally published in 1770, the writer launches forth in impassioned style the most extravagant encomiums upon this substance, which he avers to be the quintessence of the earth. Salt is here characterized as a Treasure of Nature, an Essence of Perfection, and the Paragon of Preservatives. Moreover, whoever possesses salt thereby secures a prime factor of human happiness among material things.
The French people employ the word "salt" metaphorically in several common expressions. Thus, in speaking of the lack of piquancy or pointedness in a dull sermon or address, they say, "There was no salt in that discourse." And of the brilliant productions of a favorite author they remark, "He has sprinkled his writings with salt by handfuls." In like manner they use the term un epigramme salé to denote a cutting sarcasm or raillery. Very apt also is the following definition by an old English writer: "Salt, a pleasaunt and merrie word that maketh folks to laugh and sometime pricketh." The expression "to salt an invoice" signifies to increase the full market value of each article, and corresponds to one use of the French verb saler, to overcharge, and hence to "fleece" or "pluck." Thus the phrase Il me l'a bien salé means "He has charged me an excessive price."