From Melwyn Bragg's book 'the Adventures of English' (fascinating and a reall good read)
'Perhaps my interest in English began when I was speaking at least two versions of it in my childhood. And within these two were, I suspect, something like the jumbled, shifting sound and sense of much earlier centuries of English.
I spoke a heavily accented dialect in Cumbria until I was about sixteen. There was also a considerable purely local vocabulary. Then the influence of school and BBC English began to erode that accent. The local dialect words were discarded once I began to travel out of the county, simply because no one understood them. But for years I could revert to that accent and remembered those words. Friends back home still employ some of them. They, like me, could switch into the more mainstream English when necessary. The vocabularies intermeshed, sometimes a new word rubbed out an old, it was a jumble, not at all difficult to manage, subject to teasing, snubbing, and as the old yielded more to the new, some regret.
I thought that my experience on a local and much smaller scale might bear some resemblance to the spoken English in the ninth century. To test that, I went through a Cumbrian dialect glossary to look at some of the words I used most commonly.
First, though, the accent. In the 1940s and 1950s,Wigtonians, like so many others everywhere else in small towns and villages, were still largely immobilised in one small area save when wars took off the men or emigration lured away desperate or daring families. It was still heavily influenced by agriculture and agricultural terms which had been just as common more than a hundred, even two or three hundred years before. Its accent was broad. To refined speakers it could appear coarse. Class climbers could even pretend it was unintelligible and subhuman. Yet it carried the deep history of our language and perhaps it had carried it intact for centuries in sound as well as in vocabulary. '
I think many of us remember growing up 'bilingual' - speaking one type of English at home, and another at school, or with friends.
My parents always spoke very well, with no accent, and never swore. So I learnt to speak as they do, but soon realised it was not good for may 'street cred' - so I changed it for use with friends when I was a teenager. Perhaps the other way round to most. For OH, it was t'other way round- as he didn't want his parents foreign accent.