Where does the expression he real McCoy come from?
The Real MacKay,” a phrase that appeared first in 1856 as “A drappie o’ [drop of] the real MacKay,” by the Scottish National Dictionary; the same work says that the phrase was later adopted as a slogan to promote G Mackay & Co Ltd’s whisky. The Oxford English Dictionary quotes Robert Louis Stevenson from 1883 in a letter saying “He’s the real Mackay.” In Scotland the reference is always the real MacKay (with the ay pronounced as i). In Ireland this changed to McCoy. The Irish MacKays, McCoys and Magees originated in Scotland and the Isle of Man, crossing to Ulster as Gallowglasses in the 13th century.
