OK, are you ready for this? A brief and necessarily skimpy lesson in English history and spelling:
Spelling in English wasn't fixed until comparatively recently. Shakespeare used to spell the same word in multiple different ways!
Anglo-Saxon English had been the richest language in Europe for literature (Beowulf, The Anglo-Saxon Chronicles) right up to the Norman invasion. Following that, English went underground and only truly re-emerged as a major language in its own right a couple of hundred years later, beginning with Chaucer. English had always borrowed and cribbed from any and every language around it, growing and developing all the while. Yet, in terms of the major European languages, English was very much regarded a second tier language, behind the Latinate tongues of French, Spanish, and of course, Latin itself.
But precisely because it was a work in progress, spelling had never been fixed. Therefore, you could easily see "shop" spelled as "shoppe". Equally, the Scottish word "kirk" and the English word "church" are actually identical, and are merely spelled differently because the lack of rules meant that people wrote a word as it sounded according to their accent.
The word "people" can be seen as peple, pepule, pepul, pepull, pepulle, pepille, pepil, pepylle, pepyll, peeple, peopel, poepull, poeple, poepul, puple, pupile, pupill, pupyll, pupul, peuple or pople depending on the text you come across! Pronunciation and spelling diverged dramatically as time went on, hence you would see "hath" and "doth" pronounced as "has" and "does" until the nineteenth century when the modern forms would displace the older ones completely, after centuries of operating side by side.
Now, just because spelling became gradually regularised, it doesn't mean it becessarily became simpler! As English grew in both importance and size, the presence of French words imported from the Normans were viewed as giving the nascent hybrid language a degree of style and class by a number of academics. With the stupidity that such people consistently show, some spellings were Latinised, thus "det" had a "b" artificially inserted to give this Anglo-Saxon word a Ltin look! "Doubt" suffered the same fate, and a totally unnecessary "c" was added to "victuals". Of course, the problem with this approach is that as time goes by people tend to pronounce what they see, and you will commonly hear people pronouncing "victuals" phonetically.
Now, it also needs to be pointed out that sometime between the end of the fourteenth and the end of the sixteenth centuries, English went through what is known as "The Great Vowel Shift". As spelling gradually began to become fixed, there was a major difference between written and spoken English. Up to that point, a sentence such as "I name my boat Pete" would have sounded like "Ee nahm mee bought Peht". Problem. As I say, pronunciation gradually came to follow spelling.
American spelling (and pronunciation) is largely down to a gentleman named Noah Webster. The early America was just as (if not more) proud of their native tongue being English than were the English. The concept was very much that English was the people's tongue, and his publications reflect that. "The American Spelling book" is thus one of the most influential books ever published in the English language. One of the techniques was breaking down the polysyllables into their constituent parts. Thus, pronunciation in English diverged between the UK and US, in Britain you have "laBORAt'ry", in the US "LABoraTORY".
Webster wanted to go further, he wanted to teach America to spell. The intention was to make the disparate spellings of words much more logical. Thus, favour, colour lost their "u", "waggon" lost a "g", "plough" became "plow" and so on. Some of these made sense, some were tinkering for tinkerings sake. But as with all such noble and honourable concepts, the problem was that only certain of the changes actually stuck, and thus we were left with multiple versions of the same words, leading to ever greater confusion in the English speaking world.
Just as an aside though, many of the old forms of English were retained in the US. Americans use "I guess" in exactly the same way Chaucer did, "gotten" was retained whereas it was dropped in Britain, "fall" continued in the States, whereas in Britain it was replaced by "Autumn".
She's as nervous as a very small nun at a penguin shoot.