Your question is a timely one, since July is apparently National Horseradish Month. And we like horseradish, too (Anthony Curtis himself is also of eastern European extraction and is a particular aficionado). And it seems we're not alone: According to the Web site horseradish.org, Americans consume around six million gallons of the stuff annually.
As is our custom, here's a bit of background before we get to the nuts and bolts. Horseradish is a member of the mustard family and it's as innocent as its relatives the humble cauliflower and kale, until you grate or grind the roots. That releases a compound called allyl isothiocyanate, or mustard oil, which is the stuff responsible for setting your nose on fire. Adding vinegar stops the reaction and stabilizes the flavor of this concoction, which is your basic horseradish sauce. Sometimes other ingredients like spices, sugar, salt, cream, beets, or vegetable oil are also added. It's best fresh -- as it ages, it starts to turn brown and lose its oomph.
And one final note on this fine condiment: Horseradish has long been heralded for its medicinal qualities, with uses ranging from a cough expectorant and food-poisoning antidote in medieval Europe to more recent indications that it may help prevent/combat certain cancers.
As far as the brands used by casino eateries are concerned, there's good news and bad.
The good news is that we've tracked down two of the major brands, namely Beaver Xtra Hot Horseradish (Bellagio buffet) and Atomic Horseradish (Cortez Room and elsewhere at the Gold Coast). When we sampled the latter during a recent review for LVA, it almost made our eyeballs bleed -- but in that "it hurts so good" kinda way that sent us back a couple of weeks later for more!
The less-good news is that neither brand is available via any regular retail outlet; they are, however, available online from a variety of sources, so just Google your chosen brand and find the best price.