The English tend to shorten names in speech while keeping the spelling the same. This happens pretty much all over the country. St John is pronounced S-n-g-n, and so on. One can rarely predict it. One simply has to be on the alert for how each person says a thing that's very familiar to them.
Americans and Aussies also have pronunciations that others find strange.
It seems to happen a lot with English place names. Cholmondeley is pronounced "Chumley". There is a small town near to where I live called "Slaithwaite" which the inhabitants call "Slawit" (although "Slathwaite" is commoner in the wider area). Before the 19th Century it was normal even among educated speakers to say "Lunnun" for London, and today we usually don't sound the "W" in names like "Greenwich", "Norwich", or the second W in "Warwick". I assume the British pronunciations died out in America because with time the original places back in the old country would have been forgotten, and people from outside the town would have just assumed it was pronounced it as it was spelt.
Like Worcestershire. Try saying that when you're drunk. Woo-sta-sha. "Oo" as is "cook", not "rooster". My mother-in-law was born there, although she still considers herself Welsh Australian (both parents from Swansea).
As for us Aussies, Woolloomooloo is a PERFECTLY reasonable name for a place. So is Iron Knob. Or Nar Nar Goon, Koolyanobbing, Tumbledown D!ck etc.
If you go to southeast Wales, it's even possible to mount Lord Hereford's Knob!
As for Tumbledown Dck, I lnow it sounds like a description of postcoital detumesence, but it was also a nickname conferred upon Richard Cromwell, who briefly served as Lord Protector before the restoration of the Stuart line in the mid-17th Century. It's odd that someone should have seen fit to name a place in Australia after him decades or centuries later.