Glad to see this name thread, I thought at first it was the old one.
There I came up with some half-muled explanation, so here's another one:
When counting down to blast off, the countdown gets to zero. After that point, the countdown continues - downwards from zero. I'm most definitely post-blast-off; yesterday I chuckled at how, many years ago, I was referred to as a space cadet.
Actually, the reason was exactly like WolfNippleTip - I just cleared my mind and that was what came up first. There was some reflection of the not entirely positive aspects of my character and a mild obsession with the mystical side of mathematics, so the naming process was clearly steered somehow.