Jack the lad
What's the meaning of the phrase 'Jack the lad'?
A conspicuously self-assured, carefree and brash young man; a 'chancer'.
What's the origin of the phrase 'Jack the lad'?
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'.

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.
See also: Rough diamond.
See also: 'Jack' phrases.