I hear people say something like ｾｰﾛ or せいろ when they are ready to do something, but i am not sure what is the correct word. I tried to look it up in dictionary, but i couldn't find it.
The origin is believed to be the phrase 一斉のせ , a kind of a chant used by a group of people as rhythm count when starting synchronized action.
There are other variations by dialect.