real McCoy

Meaning

Noun

• The genuine thing, neither a substitute nor an imitation.

Origin

• Corruption of Scots 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.
• {{cite-web
• |date=2001-06-06
• |archiveurl=https://web.archive.org/web/20020314063754/http://www.randomhouse.com/wotd/index.pperl?date=20010606
• |archivedate=2002-03-14
• |url=http://www.randomhouse.com/wotd/index.pperl?date=20010606
• |title=real McCoy
• |work=The Mavens’ Word of the Day
• |author=Georgia Maas
• The term is the subject of many folk etymologies, discussed at the Wikipedia entry.