Green’s Dictionary of Slang

1. an efficient, energetic, but not quite socially acceptable, person.

1883		E.J. Milliken Childe Chappie’s Pilgrimage 20: A cropper I’ve come, but it shall not be said / That this Johnny’s a cocktail blue-funked off his head.
1894		Truth (Sydney) 28 Oct. 1/2: ’E ain’t no cocktail, I bin told, / ’E uster use ’em [i.e. his fists] now and then.
1895		‘Harry on ’Arry’ in Punch 17 Aug. in P. Marks (2006) 24: And your Rads, and your Cads, and your Cocktails, all haters of Class and the Crown.

2. (Aus.) a second-rate individual.

1895		Riverina Recorder (Moulamein, NSW) 5 June 2/7: [T]he Half Holidayites are a lot of cocktails [...] they ought to have turned up for the last match of the season.
1904		Sydney Sportsman (Surry Hills, NSW) 3/2 6/3: [I]t is wonderful how such duffers and cocktails ever get into the game [i.e. boxing].

3. attrib. use of sense 1.

1838		R.S. Surtees Jorrocks Jaunts (1874) 43: No one ever saw him do a cock tail action in his life.
1838		R.S. Surtees Jorrocks Jaunts (1874) 115: JorrocksYou’ve perhaps heard tell of the Surrey ’unt? Stranger. Cocktail affair, isn’t it?