So why is someone from Liverpool a Liverpudlian and not a Liverpoolian?
The OED says: Liverpudlian belonging to (a native of) Liverpool, of which the final syll. was joc. altered to puddle.
What does the abbreviation “joc.” mean? Jocular? Puddle is funny?
Yes, jocular. Not laugh-out-loud hilarious, just a mild play on words.
And it’s far from the only such adjective which is something other than a straightforward derivation from the place name - Glaswegian, Mancunian, etc. - even if these have very different origins.
“Puddle” rather than “pool.”
Can you not see why that would be described as jocular?
A puddle is a pretty small and crappy body of water, and describing Liverpool as Liverpuddle is similar to many other examples of using a diminutive to insult or make fun of something.
I do get the joke but was surprised (bemused, maybe) because it seems to be the official term for someone from Liverpool. Official stuff is rarely funny.
Liverpudlians are okay with it? It’s not seen as dismissive or a putdown?
The alternative is Scouser.
It’s not official in the sense that anyone ever voted on it. There’s a slightly more dismissive slang word for people from Liverpool - scousers. I don’t think it’s true that common nicknames for things like this are seldom jocular. I was trying to come up with an example, but the only case I could think of was the nickname “The Big Apple” for New York, which isn’t humorous exactly but is kind of strange.
The name “Gotham” for NY (and hence Gothamite for a New Yorker) is a bit more jocular. Washington Irving coined it in reference to the Wise Men of Gotham, who acted like madmen.
Certainly “Beantown” and “Beantowner” in reference to Boston are jocular. “Sooner” for an Oklahoman is also a bit of a joke. Likewise “Nutmeg State” for Connecticut (in reference to the wooden nutmegs sold by Connecticut Yankee peddlers).
I’d venture it’s no more or even less joc. than across the pond.
It’s quite simply the adjective for a, errrm, Liverpudlian. Few will have ever heard of, let alone care about, the etymology. And they’re used to being reminded how crappy the place is, anyway 
For another example where the original disparaging nature has disappeared, here is what Etymonline has to say about Cockney:
Mancunian, on the other hand, is not one of those coinages, but rather the fossilization of a derivative of the city’s original name, Mancunium, deep in history.
TheAmerican Heritage Dictionary:
“Manchester” derives from the Late(?) Latin castra mancunium, “fortified point at the place called Mancunium,” with the transition of -castra to -chester common in English place names.
Some names are not coined with jocular or ironic intent, but still seem that way after the fact.
Anyone who’s spent any time in Baltimore can only view with some skepticism the city’s self-proclaimed status as “Charm City” and “The Greatest City in America.” Even “The City That Reads” seems rather ill-chosen, considering that Baltimore followed it up by closing down or reducing the hours of many branches of the public library system.
The latest slogan, “Believe,” at least has the advantage of being rather nebulous, and optimistic rather than declaratory.
Like Minnehopeless for Minneapolis.
Polycarp, thanks for explaining Mancunian. I’ve never run across that one.
I’m from Blackpool. As such I regard myself as a Blackpudlian although if I had been born there I would be a Sandgrown’un, Blackpool having a beach of sorts.
Just to clarify matters, people from Hartlepool are called Monkey Hangers. 
In all seriousness how many ‘pool=pudlian’ adjectives are in general use? If there’s a general pattern, then it seems to me to make the ‘puddle’ etymology rather shaky and instead would point to a general linguistic habit of reforming names in this way to place the emphasis on the third-from-last syllable. (As is also the case with Aberdonian, Dundonian, Bristolian…)
I live in northeastern Oklahoma, near a town called Bartlesville. Several decades ago, the City Council of Bartlesville decided to hold a public election to choose an official name for the town’s residents. Among the options were “Bartlesvillagers,” “Bartlesvillians,” and “Bartlesvillites.”
The winner – a term that is still used – was “Bartians.”
I find this strangely amusing. The first thing that occurred to me when I saw the word “Bartians” was this: since Martians come from Mars, is it not logical to assume that Bartians come from bars?
Haha, about the “Bartians”. I like it. And it strikes me that you had a pretty close escape from being called “Bartlevillains”. Not a good image to please the local council. OR perhaps “Bartlevilleins” for the feudally minded.
I like the Bartians, too. If for no other reason than I’ll remember it
I don’t know if my town has adopted a nickname. I’ll have to ask at the next city council meeting. I guess we could be Woolstockans. It’s cold enough to be apt.
Woolstockers sounds like the kind of people Hal Briston might hang around with.
I don’t think the logic holds here. The others were probably all formed later by analogy with Liverpool > Liverpudlian. OED seems to list only Liverpudlian, from 1833, so unless they’ve missed out on a lot of data the others must postdate that by at least 150 years.
Liiiiver-Pud- lian
Liiiiver Bird (on top of the building)
Liver Pool
Why I know that is a mystery.