Here's a little bit of D&D trivia that just popped into my mind, so I thought I'd share it.
The concept of combat advantage came up somewhat early in the 4e design process. The idea was to collapse a ton of fiddly modifiers in the core game into one mechanic. That mechanic would also serve as a flag for things like sneak attack. I don't think that's a huge leap that requires a story. The story lies in the term combat advantage.
The term combat advantage derives from Magic: the Gathering. Back around 2002 or so, I played tons of Magic with my friends Jared and Dave. We'd stay up until 2 AM at Jared's place playing the game.
As tends to happen when gamers congregate at 2 AM, we had a lot of random, weird inside jokes. One of them involved card advantage, an important concept in Magic. Whenever anyone did something to gain it, I'd say, in a the sort of voice that a robotic version of Zeus would use, "CARD ADVANTAGE!"
(My other charming habit was using creature kill or counter spells as sort of fly swatters. I couldn't just play the card. I had to smack the card I was taking out with it. Maybe there's a reason we eventually stopped playing Magic so much...)
Later, that goofy bit of idiocy evolved into a much more elaborate set-up that never moved beyond the 2 AM planning stages. We envisioned a game table with a giant, red button. When one achieved card advantage, one hit the button to activate an alarm klaxon and flashing lights throughout Jared's house. An air raid siren atop the house would sound, and a fireworks show would commence to let everyone in southern New Hampshire know that, yes, indeed, someone in Jared's gaming room had achieved card advantage.
Anyway, that term had stuck in my head for years. Combat advantage was an obvious next step from that.