"Grain of salt"

How did the term “grain of salt” come to mean a little bit of skepticism?
As in, when responding to an item of speculative information, someone will say, “I’ld take that with a grain of salt” as opposed to saying, “I’ld be a little bit skeptical of that info.” It is a colorful phrase but seemingly meaningless.

IIRC, the phrase is really old. In Latin it’s cum grano salis, meaning literally the same thing. I’ve always assumed that it meant that the information couldn’t be taken on its own (at face value), but needed some seasoning (you had to know the background i9n order to know how much to trust it and properly interpret ir).
But you know how those assumptions are – often even the logical ones turn out to be incorrect. Take it with a grain of salt.

From Word Detective:

There’s also the related Latin phrase, Sal Atticum, literally, Attic salt (that is, salt from Attica), which means simply “wit.” This, taken together with the phrase cum grano salis, says to me that the concept of a whoosh was known to the ancients.

When something seems unnecessarily expensive, some folks say, “That’s pretty salty.”