In one article, “What’s the story on secret Mormon weddings?” you use the term and it set me to wondering where that term originated.
First, welcome to the Straight Dope Message Boards, phillipmo, we’re glad to have you with us.
Second, Evan Morris (“The Word Detective”) at www.word-detective.com says:
And third, although your question is loosely tied to a Staff Report, it’s really an independent question, so I’m moving it to the General Questions forum, which is more approrpriate.
It’s at least as old as Pliny (1st. century A.D.). It still turns up in Latin as cum grano salis. Pliny speaks of Pompey the Great having discovered a universal antidote to all poisons, of which a single grain of salt was a necessary ingredient. Some doubt that this is the origin of the English phrase, because the connection is not clear, but I am not aware of any better alternative.