Green’s Dictionary of Slang

1. an easily duped simpleton.

1860		Isle of Wight Obs. (Ryde) 7 Apr. 3/4: We admire timid and gentle things [...] and public men too like agreeable soft things, and look with applauding favour on the undescerning [sic] scribe.
1890		Sporting Times 12 Apr. 2/3: Charlie Thompson won swimming match [...]. Charlie swam half-way under water, and other man never worried, as he thought Charlie had not started. Soft thing.
1900		Ade More Fables in Sl. (1960) 104: He was the Softest Thing the Lady Robber had Stood Up that Season.
1936		D. Stivens Tramp and Other Stories 26: This’s the guard who’s a soft thing, eh? ‘He’s a decent cove.’ I’ll make your tongue hang out!

2. something which requires no effort, an easy job, an easy win etc.

1865		Brooklyn Dly Eagle (NY) 24 Aug. 2/5: The Atlantics went to New Brunswick short handed, thinking they had a soft thing [...] and were defeated.
1871		L.H. Bagg Four Years at Yale 48: Soft thing, an easy place, a pleasant position, a sure chance.
1872		G.P. Burnham Memoirs of the US Secret Service 54: They had a soft thing of it.
1880		Butte Miner (MT) 27 July 3/3: Phillipsburgers supposing they had a soft thing came to Butte in full force [...] Sporting Butteites also imagined they had a soft thing.
1885		Bulletin (Sydney) 14 Mar. 14/2: According to all accounts, the slogger is carrying on a game which can’t last, and in twelve months time, bids fair to be a ‘soft thing’ for a really good man.
1890		H. Lawson ‘The Squatter, Three Cornstalks, and the Well’ in Roderick (1967–9) 1 72: And so they thought they’d got / A rather soft and easy thing.
1900		Bulletin (Sydney) 20 Jan. 24/4: Two weeks hence, Murphy meets Archer […] – apparently another very soft thing.
1911		E. Dyson ‘Dukie M’Kenzie’s Dawnce’ in Benno and Some of the Push 39: Mr. Dickson realised now that he had a ‘soft thing.’ It was plain that Cootie would take it lying down.
1926		Wood & Goddard Dict. Amer. Sl.
1940		Oshkosh Northwestern (WI) 25 July 7/2: The friend of fascism is the man who loves his soft thing more than he does his country .