The continent referred to in this quote is Australia (which means that we are talking here about the Wizards of Oz, right?), where there exists a brand of beer called ‘XXXX’ (pronounced ‘Four Ex’), produced by the Castlemaine Tooheys brewery. A New Zealand correspondent tells me that the reason the beer is called ‘XXXX’ is that if it had been called ‘BEER’ the Australians wouldn’t have been able to spell it. Ahem.
(The actual origin of the name ‘XXXX’ lies in the number of marks used by Castlemaine to indicate alcoholic strength. Most European beers today are of 4X strength, with some being 3X or even 5X.)