Green’s Dictionary of Slang

1. one who gives out or sells advice on horseracing or dog-racing; also attrib. [SE from 1900].

1852		Morn. Advertiser 1 Apr. 7/4: As we are sure to be again victimised by the notorious tipster and list-keeper of Kennington, we give our advice candidly. Tip before entry for hedging—Elthiron, Haresfoot, Kate, 60 to 1 each.
1862		Times 31 Dec. n.p.: Prophets, tipsters, and welshers – the parasites of the ring – are flourishing upon the infatuation or the ignorance of society.
1864		Western Dly Press 7 Sept. 3/4: A Table of Tipsters, price 2d, [...] containing the Phrophecies [sic] of the whole of the Metropolitan and Provincial Sporting Papers, the Latest Bettings and Scratchings.
1869		J. Greenwood Seven Curses of London 410: Not a very luxurious one [i.e. living], it would seem, judging from the shady quarters of the town from which the ‘tipster’ usually hails.
1872		Pall Mall Gaz. 13 Dec. 10/2: Le ‘Tipster’ and Le ‘Tout’. An excellent Frenchman has undertaken to make his countrymen familiar with ‘la langue du turf’.
1887		Pall Mall Gaz. 27 May 1/2: The Tipster’s Revelations [...] This morning we give [...] our tipster’s confessions.
1890		Sporting Times 15 Feb. 5/4: Who would take the ‘tipsters’’ wrong ’uns, and the ‘ramps’ so tamely.
1895		Crowe Aus. Sl. Dict. 86: Tipster, an agent who guides his supporters in betting on racehorses.
1903		A. Binstead Pitcher in Paradise 171: Jack Dickinson, the Leeds tipster, whose business it was to sell you a card whereon the potential winners of the day’s races were indicated.
1912		E. Pugh City Of The World 274: He mustn’t make no bloomer either; for it means the lag as sure as a tipster’s nap.
1922		Joyce Ulysses 449: She’s on the job herself tonight with the vet, her tipster, that gives her all the winners and pays for her son in Oxford.
1933		M. Marshall Tramp-Royal on the Toby 247: Us tipsters wot has got a following has got to keep groomed.
1937		R. Westerby Wide Boys Never Work (1938) 85: Hangers-on and rabbit-faced tipsters.
1938		J.B. Booth Sporting Times 229: The methods of the tipster — and the would-be tipster — are endless.
1948		‘Josephine Tey’ Franchise Affair (1954) 209: ‘[I]f the worst comes to the worst and they end up bankrupt, the old lady can always do a fair trade as a tipster’.
1953		A.J. Liebling Honest Rainmaker (1991) 62: The legitimate turf consultant [...] or even tipster, acts in good faith. The tout is cynical.
1956		‘Toney Betts’ Across the Board 241: He believed big money could be made with a tipster bureau that didn’t lie or pretend to fix races.
1965		F.J. Hardy Yarns of Billy Borker 59: These tipsters gradually build up a list of people who are mugs enough to pay for tips.

2. one who gives monetary tips to servants, employees etc.

1889

Pall Mall Gaz. 18 Feb. 7/3: It is not uncommon for the ‘tipster’ to pay to the employé of the purchaser a fixed commission of so much per pound or ton on all goods purchased by the master. It then becomes the interest of the servant to make his master buy as much as possible of any article from the ‘tipster’ .

3. one who gives out any form of ‘inside’ information; spec. (US Und.) a ‘civilian’ who alerts criminals to potential victims, places to rob, etc; also attrib.

1900		Sporting Times 2 June 1/1: The tipster who in May prophesied the flight of Kruger, and declared that the old Dutch would be caught by Jeune, will have a good run for his money.
1920		Ade Hand-made Fables 136: A Sample Menu recommended by Hazel McGinnis Updyke, a famous Tipster weighing between 80 and 90 Pounds.
1933		C. Himes ‘Prison Mass’ in Coll. Stories (1990) 172: The ‘tipster’ had told him where the safe was located and that it would be loaded with currency.
1949		N. Algren Man with the Golden Arm 73: His tipsters gave him head starts to hospitals.
1950		Goldin et al. DAUL 224/1: Tipster. One who points out potential victims to criminals in exchange for a share of the loot (usually ten percent) ; a professional purveyor of information about persons or places which may profitably be made the object of criminal activity.
1956		‘Toney Betts’ Across the Board 241: The tipster racket is a confidence game.
1966		H.S. Thompson Hell’s Angels (1967) 220: They were arrested [...] on an anonymous tip – which netted the tipster close to $100,000 in reward money.
1971		T. Thackrey Thief 122: A tipster is a guy, sometimes a real square-john, who wants to make a little money on the side and knows a few hoods [...] he keeps his eyes open and sees who’s got, oh, you know, money or some real classy jewelry.
1997		C. Hiaasen Lucky You 10: ‘Roddy would be your brother-in-law?’ The tipster.
2020		C. Hiaasen Squeeze Me 115: ‘Unbelievable. You, a police informant?’ [...] ‘I’m not a motherfuckin’ informant. I’m a tipster’.