"Black Friday" in retail and shopping indicates the point at which retailers begin to turn a profit, or are "in the black".
In carbon market this would mean quite the opposite. A day in November 2011 when the price plummeted below 7 EUR. It could have been hardly called "trading", it more like a sale-off, with large volumes traded on the red candles (big turnover on the slide, adding to the momentum) and low volumes on green and short candles (few traders buying-back) - compare with chart. Short-covering on Friday helped to get the carbon out of the abbys.
Today, we are higher on the back of rising EURUSD and rising hopes on the progress with EFSF. However we are struggling to mark new high (at or above 8.20 EUR) which can push us back below 8.00 EUR again.