(For the record, I didn't know! I don't know what a bong was! I'm fairly naieve.)
Well! A billabong is something else:
Billabong: Stagnant, unmoving water. (Australian.)
Australian English word meaning a small lake, specifically an oxbow lake, a section of still water adjacent to a river, cut off by a change in the watercourse, cf. an oxbow lake. Billabongs are usually formed when the path of a creek or river changes, leaving the former branch with a dead end. Despite some claims of a Scottish Gaelic origin, the word is most likely from the Wiradjuri term bilabaŋ.
I think the Washington Post, and an Old Person, owe me an apology.