The secret “anti-languages” you’re not supposed to know
bbc.com
bbc.com
Plus, of course, there are also innumerable sub- and subsubdialects based on all sorts of things that have nothing to do with locale or ethnicity---Medical-School English, Twelve-Year-Old-Males-Whose-Worldview-Is-Deeply-Informed-by-South-Park English - that are nearly incomprehensible to anyone who isn't inside their very tight and specific Discourse Community (which of course is part of their function) (authority and american usage)
Which substitution was used in an episode of Fawlty Towers, though I lack time to find the reference.