Scitis- very probably akin to gaelic Sgiath which means
wing, makes sens when you look at the island.
Is it just me or do many of the English river names look
Gaelic. It's probably not Gaelic itself, but some cognate
e.g. abhainn- Welsh afon- avon
Here's a few-
Esk- Uisge? Iasg?
Don- Donn? (Danube?)