Green’s Dictionary of Slang

1. (Aus.) a meal of salt beef and damper, i.e. a form of unleavened bread, baked in the ashes of a fire.

1848		H.W. Haygarth Recollections of Bush Life in Aus. 6: The Traveller’s entertainment is confined to the ‘old thing’, as it is contemptuously called, that is to say, beef and ‘damper’.
1945		Baker Aus. Lang. 80: It was what W.W. Dobie [in 1856] called the muttonous diet of the outback that produced the expression the Old Thing for a meal of mutton and damper.

2. a person, often as a term of address or as funny old thing etc.

1854		Thackeray Newcomes I 215: You bachelors are wicked old things!
1876		M.E. Braddon Dead Men’s Shoes I 205: I’m sure I don’t know what he wants – the nasty old thing!
1894		A. Hope Dolly Dialogues 59: I said you were a silly old thing.
1900		E. Glyn Visits of Elizabeth 15: They don’t have to get married off again at once – so why should that ugly old thing.
1903		A. Binstead Pitcher in Paradise 200: I hope that you will like the neighbourhood, dear old thing.
1911		A. Bennett Card (1974) 265: It appears as if Toronto was a sort of paradise. But you can see the old thing prefers Bursley.
1918		‘Sapper’ Human Touch 9: Jolly good idea of yours, old thing.
1923		O.O. McIntyre New York Day by Day 23 July [synd. col.] He is the sort of fellow who greets you with, ‘Hello, old thing.’.
1934		D.L. Sayers Nine Tailors (1984) 66: I don’t care a dash about that, old thing.
1945		A. Christie Sparkling Cyanide (1955) 51: But not on the phone, old thing.
1950		A. Christie Murder Is Announced (1958) 75: She’s a nice old thing.
1957		G. Kersh Fowlers End (2001) 126: The pubs are shut, I’m afraid, old thing.
1967		M. Braly On the Yard (2002) 6: Some of them old things back home would be halfway to Kingdom Come already.
1976		P. Theroux Family Arsenal 120: Norah loves them, poor old thing.
1999		K. Sampson Powder 111: Feeling pretty damned chipper, actually, Wheezy, old thing.

3. as a euph.