My father studied engineering at Battersea Polytechnic in London in the late 1940s (he graduated in 1950) where one of the lecturers was Indian or Pakistani. Now, of course, everyone in Britain is used to Indian and Pakistani accents; but this was before large-scale immigration from the Indian subcontinent to London had begun, and my father, who had spent his teens in East Africa where there was a considerable Indian population, was literally the only student on the course who could understand this man’s accent. Everyone else was begging to be allowed to borrow and copy his lecture notes.

There are many anecdotes from WWII of American soldiers in Britain unable to make themselves understood because the Brits were unfamiliar with the American accent. (And there is the classic sign, “English spoken here. American understood.") The ubiquity of American movies and television since then has erased that unfamiliarity. It’s not that the accents have disappeared, but the listeners are sufficiently familiar with them to understand.

And still, when I’m watching a British film or TV show that features heavy regional accents, I often have to flip on the English subtitles to catch what is being said. I have no such problem with RP or the more common regional accents, like Edinburgh Scots.

I remember being in London in the mid-60s shopping around for ska records and a certain other substance in Brixton. The West Indians were mostly recent immigrants and the Jamaican accent was all but unintelligible if they spoke too rapidly. Every other word seemed to be a long-drawn out ‘Raaaaassclaat’. Heady stuff and I drank it all in appreciatively. I remember when I was in the army in 1966 my fellow-clerk and good friend was Winston, who haled from Barbados. He himself had a very low opinion of Jamaicans and did a very comical impression of their speech. His own Barbadian accent was far different from the Jamaican one, far closer to standard English and British RP, although he was middle-class so caparisons are odorous, as Mrs Malaprop said.

The Brits (Poms, as we call them) never miss an opportunity to remind us that Australia was born in shame, a colony built by their worst offenders,

Truly it is said that we hate most those whom we most injure (though it must be said that by no means all Britons are so ignorant and thoughtless). Australia was a place where Britain sent all its political subversives - people who thought that Britain should be governed by someone more enlightened than that brutal dinosaur the Duke of Wellington, and that a working man (or woman, or child) was entitled to a decent day’s pay for a hard day’s work. Some of the most progressive political brains in Britain were transported, together with poachers who wanted to redistribute the nation’s pheasants a bit more equably, and the occasional pickpocket who tried to do the same with the nation’s wealth ;-)

So what is the origin of mack daddy?

It’s short for “Macintosh”, and don’t call me “daddy”.

(see here)

Okay, I saw there…

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This use was apparently popularized by an anonymous African-American song of the 1950s or earlier, celebrating (and titled) “The Great MacDaddy,” a flashy and successful pimp. This use of MacDaddy as a name is probably from the earlier mack ‘a pimp’ and daddy, as a form of address in jive talk. The term gained currency in rap music by the late 1980s or so, when it also began to spread in mainstream language.
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So where did the term “mack” meaning “pimp” come from, papa?

Try dictionary.com or merriam-webster.com, son.

Holy mackerel, I would not have guessed that. Thanks, daddy-oh. What a great world to be in, love in and laugh in.

OK.  Next question: When (and how) did mackerel come to refer to the fish?

The origin of mackerel, the fish, is uncertain. It appears in English c. 1300 in the romance Havelok the Dane (which has a passage that describes the fishing industry in some detail and is a good source for fish names). And there is an Anglo-Latin citation of makerellus from c. 1159, which is also likely from a French source. But where the French word comes from is not known. There are various explanations, all deficient in one way or another.

But the modern mack and mack daddy are probably not descendents of the older English mackerel meaning “pimp.” The older word fell out of English use for a couple of centuries, and the modern uses are probably new borrowings from the modern French macquereau ("mackerel," which can mean both the fish and pimp).