Cho

Actually, the "cho" is a pumping expression usually done with players all over the world, preferably asians too, as you can see the chinese and the japanese as well. When you say this expression, you actually pump up your mind and your adrenalines activate themselves for your body to have better reactions in the next coming points. This excites both your mind and your sensory locomotors, adding more energy and focus to your gameplay. That's why cho/yo is being exclaimed out loud because it makes the user feel happy and energetic, even if they are at the stake of losing.

Hope this helps, Nakso.

Thank you a lot! It helps a lot! :)

Your welcome. I usually do this too, it helps me calm down at the same time jittery too. Don't be afraid to pump up even at small battles.

I've heard some suggestion that 'cho' is a Chinese word. 

I notice some Korean players say 'Jo-a' which means 'good' in korean. I assume they picked this Korean word because it sounds similar to 'cho'.  

Well, whatever it is, its a pump expression. Cho for Chinese, yo for japanese, go for europeans <?>

Our coach always advices us for not yelling such words. But I don't think this advise is right. Well, I use the Spanish word 'VAMOS'!