What is the origin of the phrase...

Cum grano salis is the Latin origin of this phrase. First recorded in A.D. 77, it might refer to an antidote that had to be taken with salt to counteract the toxic effects of a substance. It might also be a culinary term, referring to salt’s ability to make a tasteless meal more appetizing. The phrase has acquired a different meaning since its appearance in English in 1647. Now it means to treat with skepticism.