Green’s Dictionary of Slang

a gentleman.

1839		H. Brandon Dict. of the Flash or Cant Lang. 163/2: Jagger – a gentleman.
1859, 1860		Hotten Dict. of Modern Sl. etc.
1864, 1867, 1870		Hotten Sl. Dict.
1873		Sl. Dict.
1881		Trumble Sl. Dict. (1890).
1882		Sydney Sl. Dict. (2 edn) 5: Jagger - A gentleman.
1895		C. Crowe Aus. Sl. Dict. [as 1882].
1906		D. Stewart Vultures of the City in Illus. Police News 15 Dec. 12/4: ‘I’ll knife the jagger (gentleman) and pitch his carcass into the well-hole’.