Why is the Thames called the Isis?

Question

Why is the Thames called the Isis when is flows through Oxford?
Who started this and why???

Answer 1

Origin of the name

The river's name appears always to have been pronounced with a simple "t" at the beginning; the Middle English spelling was typically Temese and Latin Tamesis. The "th" lends an air of Greek to the name and was added during the Renaissance, possibly to reflect or support a belief that the name was derived from River Thyamis in the Epirus region of Greece, whence early Celtic tribes are thought to have migrated. However, most scholars now believe Temese and Tamesis come from Celtic (Brythonic) Tamesa, possibly meaning 'the dark one'.

Indirect evidence for the antiquity of the name 'Thames' is provided by a Roman pot-sherd found at Oxford, bearing the inscription Tamesubugus fecit (Tamesubugus made this). It is believed that Tamesubugus's name was derived from that of the river.[2]

The name Isis, given to the part of the river running through Oxford, may have come from the Egyptian goddess of that name but is believed to be a contraction of Tamesis, the Latin (or pre-Roman Celtic) name. Richard Coates has recently suggested that the river was called the Thames upriver, where it was narrower and Plowonida down river, where it was too wide to ford. This gave the name to a settlement on its banks, which became known as Londinium, from the original root Plowonida (derived from pre-celtic Old European[citation needed] 'plew' and 'nejd,' meaning something like the flowing river or the wide flowing unfordable river).[citation needed] For merchant seamen, it has long been just 'The London River'.[3]

Answer 2

Isis was a motherly goddess figure in Egyptian mythology. She might have been the goddess of fertility, I can't quite remember. Either way, she was known for nursing her son Horus, and helping him grow. Likewise, the Thames brings life, fertility, and strength to the nearby land.