blue canary
n.— «Altschul said that the first responders to any terrorist attack would likely be police or firefighters. Like the canaries once used by miners to detect poisonous methane gas, the “blue canaries,” as police and firefighters are sometimes called, would probably suffer heavy casualties until the agent is identified.» —“Army giving cities fighting chance against chemical weapons attack” by Ron Martz Atlanta Journal-Constitution (Georgia) June 29, 1997. (source: Double-Tongued Dictionary)
Further reading
If you speak a second or third language, you may remember the first time you dreamed in that new tongue. But does this milestone mean you’re actually fluent? And a couple’s dispute over the word regret: Say you wish you’d been able...
Frederick from Valdosta, Georgia, wonders about the term galley-west. To knock something galley-west means to “knock it into confusion” “send everything in all directions.” In Mark Twain’s Adventures of Huckleberry...