I'd always believed the cocktail to be a uniquely American invention, dating back a couple of centuries. However, according to the Telegraph, that's not the case.
Until recently, the earliest-known use of the word "cocktail" in print that referenced drink was from 1806 in an upstate New York newspaper. Then, in 2005, it was discovered in a Vermont newspaper from 1803. In 2010 we found the word used in the March 20, 1798, edition of The Morning Post and Gazetteer, a long-defunct London newspaper. The paper had reported on March 16 that the landlord of the Axe & Gate tavern at the corner of Downing and Whitehall, on winning a share of a lottery, returned to his establishment and erased his regulars’ tabs with a mop “in a transport of joy”. Four days later the paper ran a satirical article listing who owed for what drinks in the heart of British politics. A certain Mr Rose (while writing letters upon the reform of public offices) owed for “gin and bitters”. Another owed for 35 nips of “glue”, “commonly called Burton ale, to make the members of the neutrality stick together”.
Toward the bottom, William Pitt the younger owed for “L’huile de Venus”, “perfait [sic] amour”, and a less French drink: "'cock-tail' (vulgarly called ginger)."
Exactly what this implied is open to conjecture. The most common use of the term “cocktail” at the time was in reference to a horse with its tail cut short to indicate it was of mixed breed. One colic remedy found in veterinary manuals from the period blended water, oats, gin and ginger.
Gingering was a technique employed by horse traders to fetch higher prices for their cocktails. A horse with a spring in its step, wide-open eyes and, most importantly, tail held high would sell for more. A well-placed thumb of peeled ginger produced the desired effect, at least until the horse was sold. Considering Pitt had recently doubled the price of the paper with a tax (the masthead read "price 3d, taxed by Mr. Pitt 3d, total 6d.") the newspaper’s editor could have been suggesting either one.
. . .
In 1869, the first British book containing cocktail recipes was published: William Terrington's Cooling Cups and Dainty Drinks. Reaching back to that first use of the word cocktail, his first recipe was for a Gin Cocktail made with brandy or gin, ginger syrup, aromatic bitters, and a splash of water.
There's more at the link.
I'm not too sure I'm comfortable with a link between horses and cocktails. After all, there's a well-known saying that weak, watery beer should be 'poured back into the horse'. If they start doing the same with cocktails, I'm outta here!