"Default" means someone being unable to do the thing they're supposed to do. If your opponents don't turn up to a darts match, they have defaulted, and so you w

"Default" means someone being unable to do the thing they're supposed to do. If your opponents don't turn up to a darts match, they have defaulted, and so you win "by default". You can just about support the computer sense by thinking that a default choice is used when a user has failed in their duty to make an explicit choice, etc. But it is a bit of a stretch. Of course, by now, the computer sense has fed back into broader usage, so it just seems like a perfectly ordinary use of the word.