Pulteney Bridge across the Avon River.
There are actually several Avon rivers in Britain. Why? The word avon means river in the old Celtic language. So when the Romans were mapping the area, they grabbed the first Celt, pointed to the river and asked him, "What's that called?" To which he replied, "Avon". "Right", said the Roman, "Write that down". They then went to the next river and asked the same question and got the same answer. By the time the Romans got to Scotland and all these rivers were named Avon, they said, "Mama mia, is this a bigga river". So Avon River literally means river river.
But this illustrates the huge difference in perception between these two peoples. To an ancient Celt, who probably never ventured further than that nearby river, there was no need to have a specific name for it. But to the Romans, who had to manage a vast empire, well of course, you name every river and stream explicitly.