I'd say "glade" is pretty rare here, and for the few who have it in their active vocabulary, it normally has nothing to do with swamps, it being an open space in a forest, what I guess we'd normally call a clearing. The dictionaries say it can be used to mean "everglade", but I have never encountered that use, or "everglade", for that matter, and I wouldn't expect to find either word outside an ecology textbook, anyway. There are the Everglades in Florida, but very few of us know why they call it that, and the word "everglade" comes from that name, not the other way around.
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