Back in the monkey days, when I was studying to be a botanist, I became intrigued with Middle English. Here was a version of our own tongue which our civilization just up and quit reading. What a loss. After all of the graduate school I could stomach, I stumbled across a hot-shot English student who gave me a copy of Chaucer's Poetry, an Anthology for the Modern Reader by E. T. Donaldson at Indiana University. I began at once studying it from cover to cover and saw why we moderns no longer had access to the language.
One barrier which had arisen over the centuries since its use was a change in vocabulary. One third of modern English consists of words never heard by people six hundred years ago, and one third of Middle English is vocabulary no longer used at all. When I set about memorizing these obsolete words, another problem appeared. Wanting to get it right, I paid close attention to the rules of pronunciation insisted upon by Professor Donaldson, which assigned completely different sounds to virtually every vowel, long and short, because of the occurrence of what he called a vowel shift (making As sound like Os and Is sound like Es) which turned Middle English into a virtual foreign language.
I put more effort into getting his pronunciations right than I did at the vocabulary. And the harder I worked, the less satisfactory it all seemed to me. As far as I was concerned, he gave no satisfactory proof for there ever having been any sort of vowel shift at all. He claimed that the way that Chaucer rhymed his verses was proof enough, but he weakened his own argument by also claiming that Chaucer and his contemporaries were sloppy rhymers. I simply could not accept such a thing out of an age of addressing court in rhyming verse.
Meanwhile, Middle English grammar kept reminding me of the Appalachian speech I grew up immersed in. Both Chaucer and the old man hoeing corn across the hedge could talk about "when he come to town." They both would say, "They was all there." But it went further than the grammar. Old timers used to say that they "was out huntin' mushyroons," and Middle English for mushrooms was musserounes. And if there had been a vowel shift, I can't imagine how it would have been possible to hang onto such a pronunciation.
In fact, how could any of these ever have existed, had there been a vowel shift? Sowynge was Middle English for sewing. Trustid was Middle English for trusted. In Chaucer's day, a thyng was a thing, just as my little girl used to be called a sweet thaing. Chaucer got fyssh out of a cryke, just like we always got feesh out of a crik. And when we chomped (champed) on these morsels, Chaucer chaumped. Het was Middle English for heated. And indeed, someone furious around home was said to be all het up, just as someone might have gotten six centuries ago over eny goode cawse. Chaucer had blewe for blue, dowte for doubt and reskew for rescue. And I swear that his verses rhyme 'way better with Appalachian vowels than with Donaldson's shifted ones.