Usage 1: "The real McCoy" is a phrase that rivals another Word of the Day, "OK" (at http://www.yourdictionary.com/cgi-bin/wotd.cgi?word=ok), for begging an explanation of its origins. Wherever it comes from, "the real McCoy" is used to emphatically assert the originality of an object, idea, or reputation.

Suggested usage: There is not but one context in which to use today's word: "Estelle swore that her silver car was a DeLorean, but when Virgil saw the doors swing outward, he knew it wasn't the real McCoy." In 1883, Robert Louis Stevenson wrote in a letter, "For society, there isnae sae muckle; but there's myself—the auld Johnstone, ye ken—he's the real Mackay, whatever." "Whatever?" Perhaps Stevenson didn't quite know if he wanted to say Mackay or McCoy, but his statement leads us toward today's etymology.

Etymology: The origins of "the real McCoy" are unclear. The top contender is a marketing jingle from Messrs. Mackay of Edinburgh, who made a brand of fine Scotch whisky that they promoted as "the real Mackay" from 1870 onward. During the Prohibition era in the United States (1919-1933), the phrase was extended to any hard liquor from Canada as opposed to lesser domestic brands. Since "the real Mackay" was already in the language, a widening of the phrase's scope in the alcoholic spectrum makes sense. Next we move from Scotch to the fightin' Irish. A popular Irish welterweight pugilist, Norman Selby (1873-1940—a life that includes the years of US Prohibition) had difficulty convincing people outside the ring of his identity. Once he floored a drunk who doubted his name and the drunk responded by saying, “That’s the real McCoy, alright,” using an Irish adaptation of “Mackay.” Selby was so impressed he changed his professional name to “Kid McCoy,” at which point he had to punch drunks to prove he was the real (Kid) McCoy. Any way you look at them, the McCoy stories point to the success of the Messrs. Mackays' publicity campaign, which means that the phrase "the real McCoy" originates in the development of public relations hype, self-promotion, and celebrity. (Thanks to Darrin Strauss's new novel, "The Real McCoy," for reminding us of today's word and to Malcolm Jones, writing for the NY Times Review of Books, for the observation about "the real McCoy" and publicity.)