I’ve heard and used the phrase ‘you may fire when ready Gridley’ and never knew it’s origin. A quick web search yielded this article from HistoryNet.com:

“YOU MAY FIRE WHEN YOU ARE READY, GRIDLEY.” : January/February ’98 American History Feature

U.S. Navy Captain Charles Gridley earned a place in history on May 1, 1898,during the Battle of Manila Bay.

By Richard Harris

Just after midnight on May 1, 1898, the USS Olympia led the United States’s Asiatic Squadron quietly through the calm, glassy waters of the Boca Grande Channel, between the island of Corregidor and the coast of Luzon in the Philippines. The United States was at war with Spain, and the American squadron was preparing to attack a Spanish fleet in Manila Bay.

As Sunday morning dawned hours later, the Olympia’s commander, Captain Charles Gridley, waited for the order to fire his ship’s guns. The order would come from the squadron’s commander, Commodore George Dewey, who watched from atop the Olympia’s flying bridge as shore batteries fired harmlessly at the advancing column of American ships. At 5:40 A.M. Dewey finally hailed Gridley with the now-famous words, “You may fire when you are ready, Gridley.”

There’s a ton more story – go read it and you’ll have a whole new appreciation for ‘Mr. Gridley’ as well some historical background on the Battle of Manila Bay.