Origin of the name 'Douglas'

[Lobsang]

I have tried to find cites online for this with no luck, but I know that the English name of the Capital of the Isle of Man, Douglas, Originates from the names of two rivers which converge at the location of the town. ('Dooh', and 'glas'). I also know that the manx name for Douglas is 'Doolish'. (So the aforementioned names of the rivers must be the English names)

But what I am wondering is, does the globally known word/name 'Douglas' originate from the name given to the Isle of Man Capital?

Oridinarily It'd seem weird me, of all people, asking this question, as youd think I'd be more likely to know than other dopers, but there are a few here who seem to have very detailed knowledge of Gaelic, including Manx-Gaelic.

[Captain Amazing]

As a personal name, Douglas probably comes from the Scottish clan of that name (Dubhghlas-black river).