diddy, n.² — Green’s Dictionary of Slang

diddy n.²

also didee

[? dunny n.² (1) but see diddy adj., i.e. the ‘little room’]

(Aus. juv.) a lavatory.

1965		F.J. Hardy Yarns of Billy Borker 56: Having the didee in the backyard isn’t very convenient.
1971		F.J. Hardy Outcasts of Foolgarah (1975) 97: In a strange place, they can’t find the diddy quick enough.
1988		J. McDonald Dict. of Obscenity etc.