Why do we say “uncle” when admitting defeat? The only facts we know for sure are that it’s strictly a North American phrase, and that it first appeared in written English in 1918. After that, opinions split on to how the custom developed. The Oxford English Dictionary mentions that it may be a variation of the Irish word anacol, which means protection or safety.
A more plausible explanation, though, dates back to the days of the Roman Empire. When young children of that era were attacked by bullies, they wouldn’t be set free until they uttered "Patrue, mi Patruissimo," or "Uncle, my best Uncle." At that time, the brother of one’s father was accorded almost the same level of status and power as one’s dad, so declaring the bully to be your “Best Uncle” was tantamount to granting him a title of respect.