:(ec) "If you translate all those other languages into English, you get British Islands." - that's because the words "isles" and "islands" have very similar (if not identical) meanings; "British Isles" would be just as valid a translation into English from most of those languages.  As for whether the islands are small or large, it depends on perspective and point of view.  Honshū for example is much much bigger than any of the British Isles and is still referred to as part of the  Japanese Archipelago.  What's more, the WP article on the subject says "An archipelago is a chain or cluster of islands." - no mention of "small" anywhere there.