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general::
Also, say the word. Give an order, tell or show when something is to be done, as in If you want us to move out, just give the word, or When you want the car, just say the word. The first expression, dating from about 1400, originally alluded to uttering a password in response to a sentinel's challenge. The second is even older, appearing in an early translation of the biblical books of Genesis and Exodus: "And God said the word to Abraham."
American Heritage Idioms