The song was written in 1911 by two Illinois students, Howard Green and Harold Hill. The school had recently discovered that its official school song, Illinois Loyalty, was not well suited to rousing a crowd during a game.
There have long been two versions of the song. Most commonly, it is played "from the hold" at the start of the chorus, when the "O" in "Oskee Wow-Wow" is held out. This version is played after first downs and touchdowns in football, and leading into time outs in basketball. Coincidentally, the buzzers at nearly every arena are in the same chord as the hold. The song used to be played "from the top" after an extra point was kicked, but has recently been replaced in favor of "Fight, Illini."
For many years, the band started playing the song "from the top" toward the end of the warmup period in basketball. When conducted correctly, the "hold" is played just as the buzzer sounds.
The song appears to have been written to be played after a touchdown, as it slows down while being played "from the top" before picking back up after the "hold."