Green’s Dictionary of Slang

(Aus.) a lavatory.

1964		B. Hesling Dinkumization or Depommification 115: Wally, taken short near Lang Park, had been picked up on the usual fake charge. [...] Even Judge Willis said on the bench that he wouldn’t be game to risk a visit to the Lang Park la-la. [Ibid.] 117: I went for a pee. [...] The la was empty except for this cove in a sports coat.
1972		A. Chipper Aussie Swearers Guide 33: You can stay at home, get shickered [...] and have a good chunder in your own loo, la-la, toot or diddy.
1977		J. O’Grady There was Kid 56: There are many euphemisms for dunnies, such as [...] loos, lalas, toots [AND].
1988		McGill Dict. of Kiwi Sl. 68/1: la/lala toilet; euphemistically short for lavatory.
1999		Eble Campus Sl. Nov. 7: la-la – women’s toilet.
2003		McGill Reed Dict. of N.Z. Sl. [as cit. 1988].