The English language is insane. It is amazing, inconsistent, simple, and difficult all the same time. So why did it end up that way? Why do we have words like Knight where the k and the gh are silent? Why do we have vowels which can be pronounced several different ways?

Of course, there are always reasons. Some are harder to explain while others are simple. Why don't we go back to the beginning...

William the Conqueror. He, leading the French Normans, conquered England at the battle of Hastings in 1066. So then French Norman mixed with Anglo-Saxon (from which England gets it's name Anglo-land). From there everything began to change. Now English had two different vowel systems clashing. The sounds /θ/ and /ð/ became <th> from <þ> and <ð> respectively. And the letter combination <gh> was originally similar to the german <ch> so it was /ç/ around front vowels, and /x/ around back vowels. And we used to pronounce those <kn> just as they do in German and a few other languages.

This added a vast amount of French (and thusly Latin) words which became mixed with the Germanic Anglo-Saxon language.  The two different spelling systems began to cause issues as well.

We had a lot of changes over time, adding in the -ynge (-ing) ending, the London dialect changed the -th in the 3rd person (he hath, he walketh, etc) into -s as it is today (he has, he walks), the devoiced <wh> /ʍ/ eventually became fully voiced /w/ in most dialects as it is today.

But the next big step was the Great Vowel Shift. This is when most of the vowels in the English language (which resembled those of modern German or French) shifted upwards. That's why ee /e/ shifted up to /i/ and i /i/ diphthongized to /aj/, a /æ,a/ shifted up to /e/. <oo> shifted from /o/ up to /u/. And u /u/ shifted to a schwa /ə/.
However, the worse part of the vowel shift was some shifted and others didn't. So when words like <keep> /kep/ shifted to /kip/ kept /kεpt/ stayed the same. Something similar happened with <bite> which shifted from /bit/ to /bajt/ and the pasted stayed /bɪt/.

So now we can see some of the many sounds have changed from their original. Although there are a lot more reasons things have changed over time, this is a start. If one has any questions, feel free to IM me at Blackkdark or contact me here.

Timothy