McCoy
noun
Mc·Coy mə-ˈkȯi 
Phrases
the real McCoy or less commonly the McCoy : something or someone that is real or genuine : something or someone that is neither an imitation or a substitute
Even though I knew it was useless I tried tugging at the bars but they were the real McCoy, solid steel.
Christopher Paul Curtis
Christopher Paul CurtisThese men refused to talk, but their taciturn, disciplined, no-nonsense demeanor indicated that they were the real McCoy. Bill Weinberg
Bill Weinberg
Word History
Etymology
alteration of Mackay (in the phrase the real Mackay), of unknown origin
First Known Use
1898, in the meaning defined above