Ok, let me nip this problem in the bud right off the bat. I do not mean “what does 1-up mean in video games ?” I know that means you get an extra life. Instead, I refer to the notation 1UP and 2UP (And on the TMNT and Simpsons Coin-op 3up and 4up). Why the letters U-P ? What do they stand for?
I seem to recall you could hit that (1UP) at the beginning and player #1 would start, or 2UP for the other guy to play. For “head to head” games opponents played one at a time. Although I may be very wrong.
Less cryptically, the convention goes back to pinball machines.
Originally there were simple lighted indicators to show which player was ‘up’ (as in ‘up to bat,’ etc,) during play. The concise “1UP” and “2UP” was carried over to the buttons, although it doesn’t really make literal sense in that context.
I got that sense Larry, from what Bill said, and you clarified it. However, if the Industry knows the meaning they are using, wouldn’t contradict itself, to have more than one player ‘up’ at the same time? (Like all of the cooperative games have)