Word.

One of the first things I loved about "The Hurt Locker" was its title.
When I saw it almost six months ago I was fascinated by the enigma behind the way the screenwriter named it.
To be honest I never quite got what it meant; was it a locker filled with pain, or was it about a damaged locker?
Forgive me for my random grammatical/existential dilemmas but both could make sense you know? Said locker could refer to the Iraq war and how it brings pain to all involved and in the second sense it could also point out how demoralizing the war has been for the US Army.
Curiously it wasn't until today that I actually did a little research to see what this meant and to my surprise-which makes me feel kind of dumb-it's apparently a very used expression in America.

hurt locker
noun - a period of immense, inescapable physical or emotional pain.
- A figurative place where someone is said to be or will be, if they are getting or expect to be getting hurt or beaten.

It apparently also means a hangover (which takes me to some awful places in terms of could've been Oscar nominees).
So as you may know English isn't my first language and as much VH1 as I watch I'll probably never have a full grasp of American slang.
But those of you who live there, have you used the expression before? Is it as common as Google said? Why do you think Mark Boal titled his screenplay that way?