Did you know that football, soccer, and rugby have a lot in common? E.g., they all have "fullbacks", defenders "tackle", they all have "off-side", each team has 11 players. The football term "touchdown" actually comes from rugby, because in rugby to score a "try", a player must touch the ball down in the end zone.

In fact, soccer is football's great uncle, in a way. At one time, soccer and rugby were the same game, simply called "football" in England. In the late 1800's, there was a split. Most people wanted to play the soccer type of football, so they became the official brand of football, called "Association Football". The rugby teams, upset, walked out to form their own sport, called "Rugby Football".

In the USA, colleges first started playing rugby football, which they called "football" for short. American soccer people got tired of saying "Association Football" all the time, so the name eventually was shortened to "soc-football" and then just "soccer".

"Gridiron" football evolved from rugby football. There are really only five major differences between the games.
(1) In football, play stops after a player is tackled. In rugby play is flowing.
(2) In football, the players huddle after each play, and they are told the preset play to run. In rugby, all play is improvisational.
(3) In football, the forward pass is legal. In rugby, you cannot throw the ball forward, only kick and run it forward.
(4) In football, the offensive team can block. This is quite illegal in rugby.
(5) In football, possession is lost if a team does not progress 10 yards in 4 attempts. In rugby, possession is usually lost either after a foul, or when the offense kicks the ball forward.

That's it! You take away just those five items: don't allow huddles and downs, no forward passes, no blocking, and no 10-yard measurements, and you have rugby!

Don't allow rugby players to use their hands, make the ball round, use a goal instead of an end-zone, and don't allow defenders to drag opponents down, and what do you have? Soccer!

Here is a graphic on how the various kinds of football evolved: