English pronunciation changed dramatically between approximately 1400-1700 in a process called the Great Vowel Shift. This explains why English spelling is so confusing today — words are often spelled the way they sounded 600 years ago, before pronunciation changed. The word 'bite' was once pronounced more like 'beet,' and 'house' more like 'hoose.' The shift happened gradually, region by region, without any central authority directing it.