<P> The expression has also been associated with Elijah McCoy's oil - drip cup invention (patented in 1872). One theory is that railroad engineers looking to avoid inferior copies would request it by name, inquiring if a locomotive was fitted with' the real McCoy system ". This possible origin is mentioned in Elijah McCoy's biography at the National Inventors Hall of Fame . The original appearance of this claim in print can be traced to an advertisement which appeared in the December 1966 issue of Ebony . The ad, for Old Taylor Bourbon whiskey, ends with the tag line: "...but the most famous legacy McCoy left his country was his name ." While the story in the ad copy bears the hallmarks of false etymology, its spread certainly reinforced a productive force tying the expression to the legacy of the inventor . </P> <P> Alternative attributions include: </P> <Ul> <Li> A dispute between two branches of the Scots Clan Mackay over who was rightful leader . Lord Reay headed one branch and he came to be known as the Reay Mackay which migrated to' the real McCoy' . See Huistean Du Mackay, 13th of Strathnaver for information abouth the dispute . </Li> <Li> Joseph McCoy (1837--1915) was mayor of Abilene, Kansas and styled himself' the real McCoy' . </Li> <Li> A Pennsylvanian named McCoy supplied commercial grade nitroglycerine to safecrackers who deemed it superior to homemade product . </Li> <Li> The Hatfield--McCoy feud </Li> </Ul> <Li> A dispute between two branches of the Scots Clan Mackay over who was rightful leader . Lord Reay headed one branch and he came to be known as the Reay Mackay which migrated to' the real McCoy' . See Huistean Du Mackay, 13th of Strathnaver for information abouth the dispute . </Li>

Where does the term the real mccoy come from