[Sorry - this is a short and rushed post. It's Week 0.]
I was reminded the other day (because I mentioned it) that I only recently discovered how to pronounce the word archipelago. As I said in that conversation, discovering how to pronounce words as an adult tends to be an embarrassing realisation that you've misinterpreted something your whole life, usually in front of more people than you would like.
In this case I suppose it's not so embarrassing, but the reason for my mispronunciation (with stress on the -la- syllable rather than the -pel- syllable) was because I was simply looking at the word as an undecomposable whole. Had I known that the word came from a Greek prefix arkhi and root pelagos (which I ought to have recognised, really, given how much I like the word pelagic), I might have had a better chance (though perhaps not, as I also pronounce pelagic with stress on the penultimate syllable).