Green’s Dictionary of Slang

(Aus.) Castlemaine XXXX lager.

1989		T. Wheeler Australia: A Travel Survival Kit 55/1: Queenslanders call XXXX ‘barbed wire’ (because that’s what the name looks like), while Victorians’ favourite beer is VB or Vic Bitter - properly known as Victorian Bitter.
1991		J.T. Pickle Aus.-Amer. Dict. 20: BARBED WIRE: XXXX. Castlemaine’s Four X Beer. Peculiar Queensland beverage.
1999		G. Seal Lingo 133: Different brands of beer have their own Lingo names: [...] Queensland’s Fourex is known as barbed wire from the jagged appearance of its trademark – xxxx.