Idioms? Not sure those exist in relation to the Olympics. Idioms are things like "He kicked the bucket", which means "He died." They're plays on words used for whatever reason. Like the person said above, though, I guess each country has their own cheers though. In English we probably say "Go team go" ? In Chinese 加油 (jia you) is frequently used.

I think that most of chants and phrases linked to all the participating countries
but not noticed that the Chinese special cheer when receiving the torch for the Olympics were a religious spiritual glorifying Lord Buddha
and does not mention the exact historical and so were the girls in the gymnastics shouting words of national and spiritual especially in China
but the reality of what China has done great in the opening the olympic Beiking 2008 is something dazzling the world ..