Isis: singular noun, from the Ancient Greek: Ἶσις (Goddess of motherhood and fertility).
Thames: singular noun, from the Celtic: Támesis (known today as the river Thames).
There is a river Thames to the north of Oxford– and there is also a river Thames to the south, but the river that passes through Oxford is known as “The Isis.” Its waters are trafficked by two very different kinds of boats. There are the riverboats: many of them still heated by fire, so that it isn’t uncommon to see wood being chopped along the bank. And then there are the rowers: boats that drain all the energy out of 8 women or men to move about as fast as the riverboats.
So: when do you say Thames, when do you say Isis? Telling someone about the lovely time you had punting on the Thames will only raise eyebrows and concern (it’s a very wide, fast river to the south of town). But if one has spent the afternoon walking along the river, saying that you took a walk beside the Isis might indicate that it took you two hours to cross a distance of three hundred yards. Trying to get around the whole problem by just calling it by its pre-Roman name, the Tamesis, probably won’t help manners.
To sound like a native, always use the following rule:
- punts, rowers, and riverboats use the Isis.
- if you find yourself in a meadow far from town and there is some water nearby, just call it “The Thames” and no one will dare contradict you.