In matters of historical context, I happily defer to my British friends. However, the term "John Barleycorn" was also used in the U.S., along with phrases such as "Who struck (hit) John?," "Demon Rum" and "Old Reliable," among many others, as a pseudonym for hard liquor - especially cheap or bad booze, which was prevalent on the frontier in the late 19th century and during Prohibition.