Hidden origins of the Philly Boy Roy accent?

[Austin From Chicago]

before babel: in search of the first language

I was watching this documentary on the evolution of language features and noticing that the scholars studying morphology and vowel sound variations between American regional dialects were doing their research in Philadelphia. Within the first ten minutes, they explain how some regional Philly vowel features such as the peculiar pronunciation of the long "i" sound in foit may have arisen in 18th and 19th century pronunciations of those sounds. Interesting stuff if you're interested in linguistics and/or Philly Boy Roy.