Posted by James Briggs on September 16, 2003
The true origin of this phrase is still a little obscure. It's first recorded in an Irish ballad of the 1880s as ' the real McKay' and is recorded as such in Australia in 1903. (McKay was a brand of Scotch whisky). We've discussed this before at https://www.phrases.org.uk/bulletin_board/8/messages/437.html We mentioned Elisha/Elijah McCoy as a possible source.
A couple of days ago I had a message from 'Jerry' (no surname given). As judged by the spelling of 'traveled', I guess he comes from the USA. He offered the following origin. I pass it on. It gives more information about Elisha and what he invented.
"Just a note: the term 'the Real McCoy' came from Elisha McCoy, a black man born in 1843. At the age of 16 he traveled to Edinburgh, Scotland, to serve an apprenticeship in mechanical engineering. In Edinburgh, McCoy won the credentials of a master mechanic and engineer. He went on to invent the self-oiling Steam Engine Lubricator. After time others started duplicating it . People wanted to know if it was a copy or the 'Real McCoy'.
The reason I know this is because I am a big steam Engine buff."
I still think the 'McKay' version is the most likely one, but the dates would sort of fit in for Elisha. Does anyone have have any kind of confirmation?