Where did behind come from?

Answer 1

In early forms of football - association, Rugby etc., when the ball was kicked past the goals, it was said to be "behind". Most early rules (circa 1860) allowed that the team defending a goal could kick the ball back into play from a specified area when the ball went "behind". This aspect of play still exists in Association Football and Australian Football.

In Australian Football, when the game transitioned to cricket grounds in the 1860s, two posts were added either side of the goal posts to mark the kickout area. Consequently, when the ball passed between the goal post and the kickout post (now called the point post) a behind had occurred.

Many year later the behinds began being reported in the results and eventually became a part of the score. At the same time the "kickout" area shrank from an area stretching from kickout post to kickout post to just the area in front of the goal posts.