I had always assumed that the horse chestnut had something to do with the horseradish, and I’m therefore deeply saddened to discover that I was, essentially, wrong. I had nurtured a lovely mental image of a proud horse tending his vegetable patch—perhaps humming gently as he weeded his radishes and deadheaded his dahlias.
Alas, botany offers little comfort. The horse chestnut has nothing to do with the horseradish, nor indeed with any other horse-related produce. The name comes from its former use in veterinary medicine: the conkers were once fed to horses to treat their coughs. Horses have historically been prescribed all sorts of botanicals—horse bane (Phellandrium aquaticum) was believed to cure equine palsy, and horse cassia (Cassia marginata) was a botanical answer to horse constipation. It is a small mercy that horses cannot write reviews of their medical experiences.
The horseradish, meanwhile, does not cure a horse of anything at all. It’s simply a big radish. In fact, that’s the whole idea—‘horse’ in this case being used in the old-fashioned sense of ‘large and coarse’, rather like horse-ant (a big ant), horse-mushroom (a hulking mushroom), or horse-cucumber (something both bulbous and disturbing).
Incidentally, radish comes etymologically from the Latin radix, meaning root. Which is also where we get radical—a word for people who want to change things from the roots upward. So, by the logic of language, all radishes are radicals and all radicals are, in some subterranean sense, radishes. This is a fact I cling to with considerable affection.