This charming expression usually implies a gent who is good with his gig and horses, but it seems if we dig a bit deeper the description goes broader:
Jack Randall’s Diary of Proceedings at the House of Call for Genius, Thomas Moore (1820) (Same definition appears in Francis Grose’s Classical Dictionary of the Vulgar Tongue)
It seems to have come in to fashionable parlance in the 1820s, as it appears again in the Parliamentary Papers, House of Commons and Command, Volume 5 (1824):
