Extract from OED Online

Jack, n.¹

SECOND EDITION 1989

ADDITIONS SERIES 1993

Add: [V.] [37.] Jack the Lad [perh. associated with the nautical theme of Jack's the Lad, instanced in a number of songs from the mid-19th cent. onwards: see quot. c1840], colloq., a conspicuously self-assured, carefree, and often brash young man; a 'chancer'.

[c1840 (song-title) Jack's the lad. Ibid. (refrain) For if ever fellow took delight in swigging, gigging, kissing, drinking, fighting, Damme I'll be bold to say that Jack's the lad.] 1981 New Society 4 June 383/3, I was always *Jack the Lad

the one everyone liked but nobody wanted to know. 1986 J. WAINWRIGHT Portrait in Shadows viii. 61 Find somebody..who..just might be Jack the Lad. 1991 Interview Sept. 50/1 The East End urchin Tony, later a Jack-the-lad and Jack-of-all-trades.