I've talked with Kevin Reylek about this. Initially, it was just a name that Alex Pandrea dreamt up - it didn't have a meaning. Kevin mentioned to me that in-house, before they were released, he was retrofitting the word to be an acronym, calling it "Nothing, Only Color". I have no idea if they ever settled on that as the official meaning, though I do remember they had a contest about it on their Facebook home page for HOPC. If you want the answer, try digging there. I think they did the contest around Holidays '12, but I can't say that with certainty. The contest wasn't about inventing an acronym but about guessing the real acronymic meaning.
I have to say, though - Nothing On Cover has a familiar ring to it. That MIGHT have been the contest winner.