Salt pouring from shaker on a black background
The Ancient Origins Behind The Phrase 'Grain Of Salt'
By David Tran
More likely than not, the phrase "grain of salt" is in your everyday vocabulary, yet the origin of the phrase may be an afterthought. Why do we advise people to take something with a "grain of salt" instead of a "pinch of pepper" or "slice of pizza?"
The phrase “grain of salt” is believed to have first originated in "Naturalis Historia" written by Pliny the Elder in 77 AD, where it appeared in a passage about an antidote for poison. Etymologist Michael Quinion suggests the phrase may have been misinterpreted as a figurative term.
Another possible origin comes from a Roman general who reportedly tried to build immunity to poison by self-administering small amounts of poison. To help ingest the poison, he was said to take the poisons with a grain of salt.
Although the idiom "grain of salt" originated in the first century, it didn't appear in the English vernacular until 1647 and didn’t become popular again until 1908. The phrase popped up in the literary journal "The Athenaeum" and was used to inflict skepticism about the qualities of photos a photographer took in Ireland.