Take it with a grain of salt. That’s what we’re advised to do when it might be wise to be skeptical of something that’s being said. But why “salt” instead of, say, “sand” or “wheat” or whatever? The answer goes all the way back to Ancient Rome, where people used salt as an antidote to poison.
There. You’ve learned something, and I’ve pushed back the teacher in me again, banishing her to…the salt mines maybe.