The great Vowel shift
The Great Vowel Shift was a major change in the pronunciation of the English language that took place in England between 1350 and 1700. The Great Vowel Shift was first studied by Otto Jespersen (1860–1943), a Danish linguist, who coined the term.
Because English spelling was becoming standardized in the 15th and 16th centuries, the Great Vowel Shift is responsible for many of the peculiarities and disparities of English spelling and pronunciation.
Because English spelling was becoming standardized in the 15th and 16th centuries, the Great Vowel Shift is responsible for many of the peculiarities and disparities of English spelling and pronunciation.
The great vowel shift saw a change in the location that we said our vowels, most prominently our long vowels, most moved up in the pallet to the top of our mouths, and originally high vowel articulation fell into the middle of our mouths, creating a clear distinction between modern English and old English, which is why it is difficult to stipulate what old English would have sounded like.