The word island was kind of a mess throughout history. The first dated attestation of it was back in the year 888, when it was spelled iland. Since then, it was also written as igland, ealond, yllonde, ylande, iegland, illond, yslelond, yle londe, and ilond. Before the muddled days of Middle and Old English, it's reconstructed to Proto-Germanic awjolanda, which could mean "meadow" in addition to "island" and traces to a combination of Proto-Indo-European hekeh, meaning "water", and lend, "land". You'll notice that none of those root words and most of the spellings I listed earlier don't have an s in them, but the modern term does. That's because of confusion with the word isle, which is an entirely unrelated word coming from the Latin word insula (you can see the conflation in yselond from before), which is pretty neat.
Adam Aleksic, a rising sophomore studying linguistics and government at Harvard University, has been described as the internet's sixth most famous etymologist. He also has disturbing interests in politics, vexillology, geography, board games, conlanging, and law.