Earlier this week, I was asked if knew what a billabong was.

Well, yes. Of course I do. But at the point at which someone asks, you know they’re asking for a reason and thus the answer you feel to be obvious is probably going to turn out wrong.

We are, by the way, ignoring the surfwear brand here.

So what do I know about billabongs? They’re Australian, obviously. They are some form of watering hole. They are a place you might go to drink.

They are, let’s be honest, a place where a jolly swagman might sit down and wait for various things to happen. (What is a swagman, anyway? That is a separate question. Banjo Patterson has a lot to answer for. And Waltzing Matilda isn’t even one of his better poems.)

As a friend of mine put it when I sprung the “what is a billabong?” question on him: like an oasis, but Australian.

I tentatively gave this as my answer. And it’s not wrong, as such. But much more specifically: billabong is the Australian name for an oxbow lake.

Oxbow lakes are, famously, one of those things everyone remembers from school geography lessons.

Can I remember what the term means? Yup.

Can I draw a diagram of the process of formation of an oxbow lake, thirty years later? Yup.

Have I ever seen one? No *.

Has this knowledge ever been in the least useful in later life? No **.

Now, admittedly the Australian climate apparently means that oxbow lakes are a rather more seasonal affair than they are in my native Britain. Even so: these two incredibly disparate concepts - oxbow lakes and billabongs - turn out just to be different local words for the same thing.

I am quite unreasonably surprised by this.