Green’s Dictionary of Slang

bung adj.2

[Abor. bong, dead]

[1900s] (Aus.) impoverished; bankrupt.

In phrases

go bung (v.) (Aus./ N.Z.)

1. [mid-19C+] (also go bong) to die.

2. [late 19C+] to become bankrupt.

3. [late 19C+] to collapse, to break down, to fail.