Green’s Dictionary of Slang

1. heavy food or an excess of drink [it fills one up].

1821		‘An Amateur’ Real Life in London I 451: In one corner lay a Sailor fast asleep, having taken so much ballast on board as to prevent the possibility of any longer attending to the log.
1907		N.Z. Truth 26 Jan. 6/8: It struck her that a hot grill qwould steady her nerves and mop up some of her swankey ballast.
1916		J. Lait ‘Charlie the Wolf’ in Beef, Iron and Wine (1917) 67: The Chief’s pet front-office sleuths slipped over to Jake’s and took on ballast.

2. money [it helps one stay ‘afloat’ and ‘on an even keel’].

1832		Westmoreland Gaz. 20 Oct. 1/4: The knife [...] was carried away too, besides a small quantity of shifting ballast that I had in my trousers.
1864		G.A. Sala Quite Alone I 39: You’ve no ballast, my boy, and you’ll founder. Take my advice, and if you haven’t laid by for a rainy day, borrow somebody else’s umbrella, and don’t give it back again.
1873		Sl. Dict.
1882		Sydney Sl. Dict. (2 edn) 1: Ballast - Money. A rich man is said to be well ballasted.
1933		C. Drew ‘Gorilla Grogan’ in Bulletin (Sydney) 26 July 40/3: ‘How about the pro-bonehead publico?’ ‘Oh, them! [...] They’re just begging to get their ballast shifted’.
1935		A.J. Pollock Und. Speaks.
1937–84		Partridge DSUE (1984) 44/1: from ca. 1850.

3. (US) a gun.

1907

W.M. Raine Bucky O’Connor (1910) 108: Del, you better relieve Mr. Hardman of his ballast. He ain’t really fit to be trusted with a weapon.

4. (US short-order) sugar.

1908

Commercial (Union City, TN) 22 May 5/1: The woman ordered a cup of coffee with cream, two lumps of sugar [...] The man wanted a cup of coffee without cream [...] the waiter ordered, ‘Cup of mud, two chunks of ballast, milk the Jersey [...] Draw another in the dark’.