real McCoy, the, n. — Green’s Dictionary of Slang

real McCoy, the n.

also the real (Sandy) Mackay, ...McKay, ...McKie, ...McKoy, McCoy, the McCoy, the M’Coy

[a variety of popular etymologies have focused on the fighting name of Norman Selby ‘Kid’ McCoy (1873–1940), welterweight champion (1898–1900) and sometime strike-breaker or ‘scab-herder’ for the Ford Motor Co. Ironically, Selby was not in fact the real McCoy, this was another, slightly older welterweight, Peter McCoy, who toured with John L Sullivan c.1885 and who killed himself after a bad loss. However the Scot. National Dict. (1870) notes that the saying, albeit spelt ‘McKay’ was adopted in 1856 (see cit.) by Messrs G Mackay and Co, whisky distillers of Edinburgh, as their advertising slogan. A further citation, as the ‘real Sandy McKay’, is found in 1873 – both Scottish uses are substantially earlier than the boxing attribution, although this may well have broadened the usage]

1. (orig. US) the genuine article, the ‘real thing’.

1856		‘Young Glasgow’ Deil’s Hallowe’en 25: A drappie [i.e. drop] o’ the real MacKay.
1873		A. Wingfield ‘The Real Sandy Mackay’ Poems and Songs 62: Faith without wark / Shows ye’re still in the dark, / For it’s no’ the real Sandy Mackay. * [...] He’s not worthy your care, / For he’s no’ the real Sandy Mackay. * [note] An expression used in some parts of Scotland, equal to saying ‘it is not the real thing’.
[1885		Bulletin (Sydney) 21 Mar. 6/2: A Melbourne paper says that ‘a subscription is being raised in Hobart to remunerate Mr. Matthew Burnett for his self-sacrificing work in the cause of temperance.’ And very proper too. We shall be proud to contribute a bottle of the real old Mackay (kept specially for the regalement of temperance lecturers who do us the honor to call on us) to the fund. [...] He should not be expected to get thoroughly sober for the rest of his life].
1900–10		Stephens & O’Brien Materials for a Dict. of Aus. Sl. [unpub. ms.] 103: MACKAY, THE REAL: pronounces Muckeye: slang term to denote absolute genuineness of purity. A dram of really good spirits would be spoken of as ‘a drop of real Mackay.’ The real thing itself, unadulterated and unsophisticated.
1901		Boy’s Own Paper 4 May 484: Giving it a good ring to show it was the real McCoy.
1903		J. Furphy Such is Life 211: [This] made us feel the station aristocracy to be a mere bourgeoisie, and ourselves the real Mackay.
1914		Sport (Adelaide) 31 Dec. 5/6: Was it lemonade, or ginger beer, / Or was it the real Macoy?
1916		T.A. Dorgan in Zwilling TAD Lex. (1993) 68: I heard the boss say you dolled up and looked like the real McCoy.
1917		Cairns Post (Qld) 3 July 4/7: Who has not heard the men from the land o’ cakes say ‘The Real Mackay’ when anything appeals to them.
1921		P. & T. Casey Gay-cat 156: It’s the real McCoy, thet idee.
1930		J. Lait Gangster Girl 25: You look the real McCoy, Annie.
1934		T. Wood Cobbers 117: Gold. The Dinkum Oil, as they say here. The Real Mackay.
1940		F.S. Fitzgerald ‘Teamed with Genius’ in Pat Hobby Stories (1967) 70: He was nothing less than the real McCoy.
1946		W. Winchell On Broadway 21 Feb. [synd. col.] Jane Pickens Waldorfing in a little number with diamond shoulder straps. The M’Coy!
1947		M.H. Boulware Jive and Sl. n.p.: Real McKoy ... Just the thing.
1949		W.R. Burnett Asphalt Jungle in Four Novels (1984) 130: This was the McCoy.
1949		D. Walker We Went to Aus. 48: This rum, and this rum alone, was ‘the Real Mackay’.
1951		‘Big Bill’ Broonzy ‘I Wonder When I’ll Get to be Called a Man’ 🎵 When Uncle Sam called me, I knowed I’d be called a real McCoy.
1951		D. Stivens Jimmy Brockett 198: It was the real McKie he was giving me.
1952		J. Jones From Here to Eternity (1998) 675: If he doesnt cool off in 21 days [...] then they figure its the McCoy and he’s not acting.
1959		H. Drake-Brockman ‘The North-west Ladies’ West Coast Stories 157: What about Matron? She’s been the real Mackay, in her day.
1961		T.I. Rubin In the Life 102: Instead of the McCoy, sometimes you get nothing but plain straw.
1968		K. Brasselle Cannibals 278: The city desk [...] and the phones were the real McCoy.
1972		G.V. Higgins Friends of Eddie Coyle 89: Far as I know it’s the McCoy. You want to count it?
1978		P. Theroux Picture Palace 254: She was just another double [...] but nevertheless bearing traces of the real McCoy.
1982		Grand Master Flash ‘Scorpio’ 🎵 Cowboy is the real McCoy.
1992		M. Frayn Now You Know 120: Jacqui’s gazing at me – she knows this is the real McCoy.
1996		(con. 1949) G. Pelecanos Big Blowdown (1999) 138: I like Robert Ryan. Ryan’s the McCoy.
2005		B. Hare Urban Grimshaw 195: Molly thought she was training Urban up and so he didn’t yet qualify as the real McCoy.
2015		N. Cummins Tales of the Honey Badger [ebook] He dropped the plastic [buttocks] and let the crowd have it with the Real McCoy.

2. (US) money.

1902		T.A. Dorgan in Zwilling TAD Lex. (1993) 68: (Mr Wise Returns From Lunnon) Waitin fer ‘McCoy’ from home.
1905		T.A. Dorgan in Zwilling TAD Lex. (1993) 68: (Handicap Horses Tell TAD Secrets) Plant your McCoy where its bound to get bigger.