A-hundred-and-ten-percent Definition
noun
(idiomatic, US, sports, informal) A level of effort exceeding one's sustained capacity, possibly risking injury.
"We busted our tails and won, we gave 110%".
Wiktionary
(idiomatic, colloquial) The exertion of more than seems possible, hence 110%, not 100%, the usual maximum amount possible.
Wiktionary
Origin of A-hundred-and-ten-percent
Based on the metaphor of operating a machine at higher than its rated capacity or exceeding the normal maximum of some rated parameter such as speed or temperature.
From Wiktionary