In Newcastle, what does?

Question

under lyme mean, or ashton under lyne.

Just curious

Answer 1

Wikipedia says ...

The Newcastle part of the name derives from being the location of a 'new' castle, built in the 12th century by. The Lyme section could refer to the Lyme Brook or the extensive lime forests that covered the area in mediæval period

but the "under" part has always intrigued me too ... you get the name of rivers in lots of place names, such as Newcastle-upon-Tyne, Stoke-on-Trent etc ... so why is it "under" ... did the river flood a lot?