This has to be American and probably cowboy in origin eg Billy the Kid, the Sundance Kid, Kid Curry (who rode with Sundance) etc and I would guess it is from age or youthful appearance though I cannot find this attested to online in a cursory search. (The poetic name Sundance turns out to be from his spending 18 months in Sundance Jail in Wyoming says wikipedia.) Could anyone have gotten such a nickname at this time or just felons?
David Maurer in The Big Con lists early 20th century American conmen such as the High Ass Kid, Yellow Kid Weil, the Sanctimonious Kid, the Hashhouse Kid, the Christ Kid, and the Honey Grove Kid. These people are probably not all youngsters so the appellation may have acquired ‘outlaw chic’ by this stage. Various rappers call themselves Kid something too in a similar romanticising process I’m guessing.
White music has the ageing Kid Rock and there was a Canadian radio DJ in the UK in the ‘70s called Kid Jensen from his youthful looks and coolness though he dropped this later, hopefully out of embarrassment. Steely Dan has a song Kid Charlemagne from the ‘70s.
Your thoughts, if any?