This week's old timey word (or phrase) is "the real McCoy." A phrase used to describe an authentic item or genuine article, "the real McCoy" dates to the second half of the 19th century. While there are at least ten different explanations for the origins of the phrase, its first known use was by the Scottish Whiskey manufacturer, Mackay. In 1870, the Mackay company started promoting their Whiskey as "the real Mackay." Pronounced "Mack-eye" in Scotland, the name spread to Ireland where it evolved into "McCoy."
Next time you are inclined to inquire about an item's authenticity, why don't you ask if it is the real McCoy?
As usual, here are some of the images I discovered while searching.