Green’s Dictionary of Slang

(Aus./N.Z.) an untrustworthy, unpleasant person.

[1838		J. Grant Sketches in London 64: ‘You blundering blockhead, you nineteenth part of a man’ shouted his lately slumbering adversary].
1885		Bulletin (Sydney) 9 May 22/3: ‘I consider this meeting not a meeting of men – (‘Lay in, Pikey!’ and laughter) – but a meeting of ninteeners – (uproar) – and the snidest and ugliest nineteener in all this snide and ugly meeting – (uproar) – is – is – the party with the entrails – (laughter) – in the chair.’.
1895		C. Crowe Aus. Sl. Dict. 52: Nineteener, a sharper or loafing fellow.
1908		Bulletin (Sydney) 3 Sept. 26/4: He gazed moodily at his empty pewter. ‘And he refused to deal?’ I chipped. Treloar sighed like a punctured tyre. ‘’E dealt with Bill orlrite,’ he said. ‘Twig ’is lamp! Jest our stinkin’ luck ter strike er rotten nineteener like ’im. Lend us one an’ er kick, an’ I’ll shout.’.
1945		Baker Aus. Lang. 138: We are [...] originators of the following terms for various sharpers, tricksters and others who live by their wits: [...] lurk man, nineteener, piker, rorter [...] and amsterdam.