Perhaps it was simply an available letter, as saghm said, but I've always imagined that at least part of the origin story is that it's a mnemonic for "invert" or "negative".
On an earlier page[1] the author mentions that they at one point "designed a more complex backplate which included […] a built in micro SD card reader, that you could read directly by plugging in a micro USB cable", among other things. Unfortunately, they go on to lament that this made the watch comically thick. As you say, the strap might be a good place to cram a USB interface without bulking up the watch body.
Right on the money. curses needs to die and we need to make better use of our resources. It's eye-opening to explore these projects that "never caught on" even though they had great ideas that we still don't see today. (Granted, those projects truly never gained popularity for other reasons.) I'm glad to see that there are others thinking about these things. The current state of things bothers me enough that I will do something about it, but I'm afraid that I am something of an extremist and that my particular solution won't satisfy many other people. Because of this, I expect more popular alternatives to arise while I am hacking my own.
> I don't think allowing websites to use specific font names in CSS was ever a good idea.
I'm with you there. I can't help feeling babied when I visit most websites these days, for more reasons than simply the commonplace (over)use of web fonts.