Pinch of salt
Q From Mark Lipman: I was wondering where the expression take it with a pinch of salt came from?
A There are two standard versions of this idiom, the much older one being grain of salt. Both suggest a need for scepticism or reserve in believing something you’ve been told: “Take everything she says with a pinch of salt — she’s unreliable”.
The expression has been used in English since the seventeenth century at least. It’s puzzling to us now because it’s based on a misunderstanding of a comment in a Latin document nearly 2,000 years old. Around 77 AD, Pliny the Elder wrote in his Natural History that the Roman general Pompey had discovered something odd a century before when he conquered Pontus, a country on the shores of the Black Sea, at the time a formidable rival to Rome. On searching the private apartments of the king, Mithridates VI, Pompey discovered that the king had built up his famous immunity to poisoning by first fasting and then taking doses of a mixture of poisons until he was able to tolerate lethal levels. (This is the origin of mithridate, an antidote to poison.)
Pliny wrote that the king had taken his doses of poison with the addition of a grain of salt (“addito salis grano” in his Latin). He meant this as a simple report. But later readers thought he was saying that one shouldn’t necessarily believe this story about a king who had been a notorious enemy of Rome. Modern scholars say there’s no evidence in Latin literature of writers using salt as a figurative expression of scepticism. The Latin tag usually taken to be the original, “cum grano salis”, is very likely to be medieval Latin.
But there is a sort of rationale to the idiom even if you discount the Plinian link. Someone who says this to you could be taken to suggest that if you’re really intent on believing what you’ve been told, then taking a figurative pinch of salt with it will help you to swallow it, just as taking a literal pinch with your meal makes it taste better.