take something with a pinch (grain) of salt
idiom

- to not completely believe something that you are told, because you think it is unlikely to be true

Cambridge Advanced Learner's Dictionary

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ORIGIN

According to many etymologists, the expression "take it with a pinch of salt" is based on a misunderstanding of a comment in a 2,000-year-old Latin document. Around 77 AD, the Roman philosopher Pliny the Elder incorrectly translated the description for a poison antidote to mean that it should be taken with a grain of salt.

The implication was that the effects of the poison could be moderated by adding salt. In fact, the original author of the document meant that salt was just one of the ingredients of the poison (in addition to two dried walnuts, two figs and 20 leaves of rue, a type of shrub).

Despite this misunderstanding, there is still some logic to the expression. If you are skeptical about something you are being told, then figuratively speaking taking it with a pinch of salt helps to swallow or digest it.

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SYNONYMS

take it with a grain of salt, don't believe everything you hear, view that with some skepticism

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SMUGGLE OWAD into today's conversation

"That data comes from an unreliable source, I recommend that you TAKE IT WITH A PINCH OF SALT."