Noun
- (idiomatic) The genuine thing, neither a substitute nor an imitation.
Origin
Corruption of Scots the real MacKay, this latter attested in 1856 as “A drappie o’ the real MacKay” (A drop of the real MacKay).
How “MacKay” became “McCoy” is unclear; first attested in the form “McCoy” in the US in 1908:
- I took a good-size snort out of that big bottle [of furniture polish] in the middle....Have you none of the clear McCoy handy around the house?
The term is the subject of many folk etymologies, discussed at the Wikipedia entry.
