Green’s Dictionary of Slang

1. (US Und.) in the context of gambling or horseracing, guaranteed to produce a profit for the organizer (usu. through corrupt ‘fixing’ and thus synon. with ‘crooked’).

1881		Salt Lake Herald 14 Aug. 8/3: Pools were sold on ‘Midnight’ at 200 and ‘Ford’ 90, sure-thing men investing liberally at the long end.
1886		letter in Miller & Snell Why the West was Wild (2003) 439: Outrages have been so frequent that the saloon element is in rebellion against the ‘Gang’ or the sure thing confidence games & holding up crowd.
1888		River Press (Fort Benton, MT) 12 Dec. 4/1: The Butte Miner is vigorously fighting the ‘sure thing’ games and the ‘sure thing’ men who are running them.
1896		Whichita Dly Eagle (KS) 26 Sept. 5/3: It is said that on form Surething Dick should win as he is in splended condition.
1901		Frank Leslie’s Popular Monthly LI 212: I saw one man lose $6000 before he realised he was ‘bucking a sure-thing game,’ and if he had wanted satisfaction he stood a poor show.
1902		Wash. Times (DC) 14 Sept. 10/3: When a ‘sure-thing man’ [...] induces you to try his game, he ‘hands you the bull con’.
1914		M. Glass Potash and Perlmutter 139: That afternoon there was a sure-thing mare going to start over to Guttenberg.
1939		Howsley Argot: Dict. of Und. Sl. 50: sure thing man – a gambler who operates a ‘sure thing’ game.
1940		D. Maurer Big Con 5: His business was sure-thing gambling.
1974		Glaser & Adams Hbk Criminology 313: Circus grifting consists of sure-thing gambling: the shell game, the blower, the bucket game, the milk-bottle game, the nail game, slum skillo, the spindle and numerous other games of chance which are controlled by foot levers and assorted mechnical devices.

2. of an individual, usu. a gambler, only willing to participate in gambling when they are certain that the odds are stacked in their favour, e.g. by playing with crooked cards; the implication is that they would not otherwise gamble and the term is synon. with ‘cheating’; also of a situation, certain to produce winnings.

1885		Butte Miner (MT) 14 July 4/2: The city [...] has been infested by a gang of disreputable characters known as sure-thing men.
1894		Report of N.Y. State Committee on Police Dept. II 1821: ‘Yes, sir; “sure thing” gambling.’ Q. ‘You never gambled, except in what you regarded as a sure thing?’.
1896		Ade Artie (1963) 9: You never see such a sure-thing crowd in your life.
1903		H. Hapgood Autobiog. of a Thief 246: A man named ‘Muir,’ a mean, sure-thing grafter, came to the stir on a visit to some of his acquaintances.
1910		H. Hapgood Types from City Streets 317: I’m too good a gun to do any sure-thing work.
1920		H.C. Witwer Kid Scanlon 173: I was nothin’ but a sure-thing player.
1928		J. Callahan Man’s Grim Justice 28: A crooked, sure-thing, heads-I-win-and-tails-you-lose card man.
1938		H. Asbury Sucker’s Progress 247: Although the sure-thing artists were vastly in the majority, there were a few gamblers [...] who were notorious among the sharpers as ‘square players’.
1945		J.R. O’Hare Socio-Economic Aspects of Horse-racing 42: It never occurs to them to stop and think they are playing the other fellow’s game; that the bookmaker is no gambler, but a sure-thing player.
1947		D. Maurer ‘Argot of the Three-Shell Game’ in AS XXII:3 165: The outside-man nudges the mark, raises the shell slightly, and shows the mark that the pea is there. It is a sure-thing bet.
1952		D. Maurer ‘Argot of Pickpockets’ in Lang. Und. (1981) 254/1: sure thing grafter n.phr. A mean, cautious petty thief: one who takes no risks and plays for small scores.
1994		V.C. Andrews Ruby 47: ‘Gib Landry, was a sure-thing player. Know what that was?’ he asked. I shook my head. ‘A player who never lost because he had marked cards.’.

3. in non-gambling senses, predictable.

1911		Railway Carmen’s Journal XVI 380/2: The short of it is that the game of law is a sure-thing game — like the bucket shop business.
1952		J. Jones From Here to Eternity (1998) 181: Like a senator sticking his rider on a sure-thing bill.
1990		(con. early 1950s) J. Ellroy L.A. Confidential 135: A sure-thing case unraveling into a shitload of possibilities.

4. of an individual, dependable, e.g. as a supplier of drugs or sex.

1953		‘William Lee’ Junkie (1966) 35: I had one of his sure-thing croakers reach for a telephone on me.
1980		A. Maupin More Tales of the City (1984) 83: Two sure-thing dental receptionist students.