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1.
A liternal translation from chinese is "fill more gasoline in your car".

Now general meaning is a friendly and cheerful shouting for encouraging athletes or players to have a better performance in competitions.
This word emerged in 2008 Summer Olympic games in Beijing.

e.g. When I heared the crowd shouted "Jiayou, jiayou, jiayou..." in stadium, I knew 100-meter final run began.
by Sheng Wang August 31, 2008