서울 (seoul) = Derived from the Korean word "서라벌(Seorabol)", it means capital city. Also, Seoul was a common noun referring to the capital of the country.
Berlin - medieval city, from Polabian "Birlin"/"Berlin" = "swampy place".
Bonn - shucks if we know. Was already called "Bonna" by Tacitus in AD 96, likely taken from Celtic roots, though there were later times the place name ... uh, went through *mutations*. (As in, called "Verona" in part of the Middle Ages.)
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