<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>

Where did the phrase the real mccoy come from