: A quick search through the archives shows that, prior to '07, sandbox meant a
: style of gameplay, like how GTA is a sandbox game. I suspect the current
: usage rose with Bungie, where they were talking about the "Brute
: sandbox". Afterward, the community generalized the term to refer to
: any faction's set of weapons.

I thought that a sandbox was the some totality of all the fun things that you could do and use in a game.

I thought that the term game from a child's sandbox - a shallow box filled with sand that children play in. (Maybe they are an American thing because I've never seen one in the UK.)

So the game is, metaphorically, a sandbox in which you play. The weapons are part of the sandbox but so is the physics system, the AI, etc.