> I assumed that Mold derived from the Welsh "moel"
> meaning a bare hill. Is there such a hill there?

It looks like the name 'Mold' is a very corrupted form of the name 'Mohaut', which is a Norman name. The BBC web site says...

"The conquering Normans gave the name Mohaut (written as Mont Alto - High Hill) to the prominent hillock known as Yr Wyddgrug. Here they built a succession of wooden castles that were, on numerous occasions, laid siege to or burnt to the ground by the Welsh."

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