Mostly I think the strange spellings are strange to us because those spellings come from another language and were incorporated into our English.
I have always been fascinated with this subject and I did a term paper in APE (advanced placement english) in high school on the affect on the language the celts had and the other conguering tribes and countries on England's language. It started as far back as that as for words being added to the English language. when you look at a dictionary a lot of them will give you the origin of the word or phrase. I find it really interesting to understand how we acquired the words we use everday.