Well, one would think it would be: "Under the Anheuser Busch," but it is indeed "Anheuser Bush." My American corporate history doesn't extend to knowing when the Budweiser merger took place.

In any event, this is the original song, by Sterling and Von Tilzer. The English music hall hit, by Florrie Forde, ("Down at the Old Bull & Bush") is an adaptation of the American original. Swallow your national pride, O ye Brits.