Black box refers to any box whose contents are of a technical and not easily explained nature. Input goes into a black box and produces an output, but the internal workings are complicated enough to be a mystery to most.
Back when airplane black boxes were invented, the internal workings were highly advanced and therefore, earned the name 'black box' for the complex way the took and stored data in an indestructable manner.
The CVR and the DFDR are bight orange or red for visability after a crash.
Here is a link that might help you a little...
Wikipedia's Definition of the Black Box
For some, the sky is the limit. For us, it is only the beginning... -- Jack Hunt