|And apparently Hiphop.|
There are some debates on whether Jok-gu is an original Korean sports or just some sports copied off another. I've read some claims saying that Jok-gu is just a Korean rendition of Sepak Takraw, and so on. However, according to Sports Encyclopedia, Jok-gu's origin goes all the way back to the Three-Kingdom Era(4th~7th century). So perhaps they have different roots, or maybe back then everybody played this kickass sports in their ancient times. Who knows.
The modern version of Jok-gu was invented in 1966, in Korean Air Force 11th Squadron. So it was invented before football tennis, I think.
How to play
Rather than going over every rule, I'll just make it simple. It's like tennis/volleyball. Almost exactly. Except you play with your foot and head. 4~6 people on each side, depending on how big the available court is. Think volleyball rules, except balls can bounce once before you need to catch it. People usually use a volleyball to play the game, but they actually have official Jok-gu balls available (and leagues too).
I've only played Jok-gu in Korean military and Korean middle school... so I never thought they actuall had official rules for this game. But apparently they do. If you're curious (and can read Korean, check out that sports encyclopedia link.
How widespread is this game?
This game is generally very popular in Korea regardless of age range. They have official leagues and tournaments annually and there are many many official teams just like baseball and basketball. I hear there are leagues in California too, with slightly different rules.
Check out the video for some Jok-gu goodness.