I live in the Cork suburb of Douglas. In Irish this is Dúglas but before the spelling reforms it was Dubhglas (which, incidentally, is still used by our local GAA club to this day). Assuming that the Irish place name came first, I'm puzzled as to how we ended up with 'Douglas' in English. Surely the Munster pronunciation of Dubhglas should have yielded something like 'Dovegloss'. It's as though the British Army cartographers had a Connacht man doing the anglicisation!

Ní dóigh liom é, nuair is comhfhocal atá i gceist.

Bheadh dúghlas ceart ó dheas ansin leis, sílim.

I would have thought it pronounced like 'dúlas' as Aonghus points out. Anglicization often went on the written word, not speech, Just because it is anglicized one way, does not mean it has a strong relation to the original.

It is true often that the -bh ending was not pronounced with a v sound in many dialects of Irish..thank God for diversity even if it causes confusion with the standard pronunciation we learnt in school..

Duffy Dubhthaigh
Dublin Dubhlinn
Douglas(Isle of Mann) Dubhghlas
Dougal Dubhgall

etcetera etc

The reason you have the ú sound is that the g became a gh, and then the gh wore away, lengthening the prior vowel.

Duffy is with an f because the 'th' became a h which devoiced the bh to an f...

I think 'Dublin' came about from non-Gaels not seeing the ponc and saying a b instead of a 'bh'

Fergus Ferris Fearghus
Angus Guinness Aonghus

So many examples..interesting...

No one mentioned that Douglas is the name of the capital city of the Isle of Man which is spelled in the Manx as "Doolish".
I just saw a photo of the city's bilingual welcome sign,

"Welcome to the BOROUGH OF DOUGLAS" and beneath that
"Ta Balley Corpagh Ghoolish cur failt erriu"

("How Are Things in Corpagh Ghoolish?" sung to the tune from Finian's Rainbow)

Fergal Farrell Fearghal