Jack the Lad.

Meaning
A conspicuously self-assured, carefree and brash young man; a 'chancer'. 
Origin
The earliest use of the expression came in an 1840 song Jack’s the Lad, with such descriptive lines as:
If ever fellow took delight in swigging, gigging, kissing, drinking, fighting
Damme, I’ll be bold to say that Jack’s the lad.
Who was Jack? Was he an real person? No one knows. It may be that 'Jack' was taken as a suitable generic name when the expression was coined, along the same lines as 'Jack of all trades' and 'Jack tar'. 
If Jack were an actual historical figure the most obvious candidate would be the celebrated Jack Sheppard, the 18th century thief who was caught and imprisoned five times but escaped four times. in the process becoming a popular hero. He certainly had the credentials to be a real Jack the lad, having made audacious escapes and recklessly carefree robberies. Unfortunately for him, he was guarded day and night during his fifth incarceration and was hanged at Tyburn in November 1724. He was 22.
Sheppard's exploits inspired pamphlets, ballads, plays and engravings, not least the portrait of him made by Sir James Thornhill, serjeant-painter to the crown, in the lad's condemned cell.