It was customary to dock the tails of horses that were not thoroughbred ... They were called cocktailed horses, later simply cocktails. By extension, the word cocktail was applied to a vulgar, ill-bred person raised above his station, assuming the position of a gentleman but deficient in gentlemanly breeding. ... Of importance [in the 1806 citation above] is ... the mention of water as an ingredient. ... Låftman concluded that cocktail was an acceptable alcoholic drink, but diluted, not a "purebred", a thing "raised above its station". Hence the highly appropriate slang word used earlier about inferior horses and sham gentlemen.

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