Origin of 'deals'

A "deal" is ATC slang for an operational error (when two aircraft "lose separation" and fly too close to one another, in violation of FAA regs). It's a very serious charge, one that no controller wants to be responsible for. Not too sure of the origin; ATC slang has developed over many decades, and many of the terms have been in use for that long.

I assumed that a "deal" was any situation that the controller needs to "deal" with immediately to prevent a collision. Again, this is just my assumption, but I can see it as a very plausible origin of the term.