the real McCoy

Something that is genuine, authentic, or exactly what it is claimed to be; the real thing. The origin of this phrase is not definitively known. A: "The traveling salesman said this diamond was the real McCoy!" B: "And you believed him?" Boy, that superstar lawyer they brought in is the real McCoy. She's the one who took down Big Oil in court!

an authentic thing or person. Of course it's authentic. It's the real McCoy.

Also, the McCoy. The genuine thing, as in That painting's not a reproduction-it's the real McCoy. This idiom has a disputed origin, but the most likely source is its use to distinguish welterweight champion "Kid McCoy," the name used by Norman Selby (1873-1940), from other boxers using his name to capitalize on his popularity. [c. 1900]

If you describe something as the real McCoy, you mean that it is the original, rather than a copy, and is therefore the best. Most smoked salmon on the market is pretty nasty stuff but this was different — this was the real McCoy. Unlike some other products which are promoted as the real McCoy, this is a genuine Indian product. Note: There are several suggestions about who the original `McCoy' was, including an American boxer, a liquor smuggler, and a Kansas cattle dealer. However, it is more likely that the expression was originally British, and that `McCoy' was originally `Mackay'. There was a 19th century whisky manufacturer called Mackay who advertised his product as `the real Mackay' to distinguish it from other brands with similar names. Alternatively, the expression may come from a dispute between two branches of the MacKay clan over which was older. Eventually the MacKays of Reay, or the `Reay MacKays', won the dispute.

The genuine article. This term probably originated in late nineteenth-century America, when a young boxer named Norman Selby changed his name to Kid McCoy and began a spectacularly successful career in the ring. For years he averaged a fight a month, winning most of them by knockouts. Hoping to capitalize on his success, numerous other boxers adopted the name Kid McCoy, but on March 24, 1899, the real Kid, in a now legendary bout, finished off Joe Choynski in the twentieth round. The next day’s headlines in the San Francisco Examiner proclaimed, “Now you’ve seen the real McCoy,” and that description stuck. In real life McCoy was actually a con artist and criminal. But in 1904 the New York Evening World said, “Notwithstanding the hullabaloo of his life and the mischief of his legend, McCoy with his wondrous speed and guile may be the first, greatest gentleman of this fresh age” (quoted in a review of a novel based on McCoy’s life, New York Times, June 6, 2002). Although this etymology is more or less verifiable, there are several other theories as to the term’s origin. Chief among them is that a Scotch whiskey made by the MacKay company was called the real Mackay or McCoy.

The genuine article. No one is certain how “McCoy” came to stand for authenticity. It may refer to a Scottish clan leader named McKay; a prizefighter named Kid McCoy, who had a rival with the same name; or a bootlegger whose wares were what he claimed they were.