Proper noun
the Great Vowel Shift
(phonology) A major change in the pronunciation of the English language, affecting the sounds of long vowels, that took place in England between 1350 and 1700.
Because English spelling was becoming standardized in the 15th and 16th centuries, the Great Vowel Shift is responsible for many of the peculiarities of English spelling.
However, the Middle English spellings were retained into Modern English while the Great Vowel Shift was taking place, which caused in some of the peculiarities of Modern English spelling in relation to vowels. Source: Internet
For English, this is partly because the Great Vowel Shift occurred after the orthography was established, and because English has acquired a large number of loanwords at different times, retaining their original spelling at varying levels. Source: Internet
Modern English is somewhat distanced from the language of Chaucer's poems owing to the effect of the Great Vowel Shift some time after his death. Source: Internet
Northern English and Scots The Great Vowel Shift affected other dialects as well as the standard English of southern England but in different ways. Source: Internet
The changes that happened after 1600 are not usually considered part of the Great Vowel Shift proper. Source: Internet
The French names (from which the English names are derived) preserve the qualities of the English vowels from before the Great Vowel Shift. Source: Internet