So, it seems I never actually wrote anything in this thread? I think?
Most things that I found weird about English over the years were not that interesting, I imagine, to most people, because I used to have a very... technical interest in the inner workings of the language and those are not that immediately fun and bizarre without foreknowledge (or a long-winded explanation).
But, there's one thing that has to do with language evolution and is still bizarre and worth sharing. It continues to completely blow my mind years after I've learnt it.
The words "isle" and "island" are not connected via etymology at all. You might assume that one is derived from the other (shortened for example). You might also assume they are similar because they entered the English language from the same source, at different times and they are different because the first changed by the time the second was borrowed (like "chivalry" and "cavalry", which ultimately come from the same word - the French for "horse").
Nope. The words are totally unrelated. Despite the fact that they sound very similar and mean almost the same thing. They are derived from two different langauge groups - and the words they come from are not even similar semantically!
"isle" comes from Latin "insula". The word itself might be etymologically connected with older words for "ocean". A similar word survives in modern English in "peninsula".
"island" comes from proto-Germanic and is historically connected with the same root as the modern word "land" (not surprisingly). It has nothing to do with Latin, with ocean, or the word "isle".
I know this sounds mildly interesting probably, but to me it's utterly crazy and almost incomprehensible - the scale of coincidence in play here. It's like convergent evolution in biology (y'know, how octopus eyes are amazingly similar to mammal eyes, despite evolving completely independently). But in biology, the similarity in form follows similar function. There's a reason for things to look similar. In language, there's no inherent reason for words to sound a certain way.
Two words looking like they are closely related and describing the same concept which are derived from completely different languages *and* words for completely different concepts? I think it's, linguistically, the weirdest thing I've seen, or will see, in my entire life. Certainly in top five.