There is a common (IMOE) English idiom, "take with a grain (or pinch) of salt", meaning one should be skeptical about the information it accompanies. Many times in the last year I've heard others try to exaggerate the meaning by changing the amount of salt in the idiom, for example:
- "I heard that restaurant is bad, but take it with a huge grain of salt"
- "Parking in that part of town isn't difficult; take it with many grains of salt"
- "Take it with an extremely tiny grain of salt, but my friend hated that movie."
I've understood this idiom to originate from an old antidote recipe, either real or allegorical. In this context, I don't understand how changing the amount of salt in the idiom changes its meaning. From conversational cues, I can sometimes distinguish whether the person means (1) "this isn't just hearsay, it's very unreliable" or (2) "I trust this source a lot, so it might be incorrect, but I doubt it". Many times, I cannot tell how the person means to change the idiom.
Question: Is there an explanation for the origin of this idiom which allows its meaning to change with the amount of salt described?
Follow-up: Is there a common understanding of the variances I've listed that have simply never been explained to me? E.g., more salt correlates with more suspicion warranted or vice/versa?