What was the “Great Vowel Shift” and why did it happen?

Cecil replies:

That’s because there isn’t any explanation. As Robert McCrum et al. note in the book version of The Story of English, “phrases like the famous ‘Great Vowel Shift’ [are] hardly more informative than the ‘unknown land’ of early cartography.” What happened was that between 1350 and 1550, the period in which Middle English became modern English, vowel pronunciations changed dramatically. The Middle English long i, formerly pronounced like the e in he, shifted to i as in high. Middle English hous, pronounced “hoose,” changed to the modern house. The experts say the GVS “in effect moved the long stressed vowels forward in the mouth,” but to me it just sounds like you open up your mouth more. Why it happened no one knows.

Cecil Adams

Send questions to Cecil via cecil@straightdope.com.