At first glance, you can tell that the word icicle has the term ice in it, but what is the -icle part? Well, first we need to go back to the Middle English word isykle. Is- is indeed the precursor of ice, from Old English is. Ultimately, it comes from the Proto-Indo-European root heyh, "frost" (through Proto-Germanic isa). A dull etymology, but now we look at -ykle! Surprisingly, it too meant "ice", which means that icicle actually is a tautology secretly meaning "ice ice"! -Ykle is from Old English gicel, from Proto-Germanic jeko (which meant something more like "clump of ice"), which in turn derives from the now-familiar Proto-Indo-European term heyh, as well. When the word icicle was first attested in the fourteenth century, it seems that the latter part of the word was already becoming archaic, and this one remnant has survived. The word popsicle, which obviously is rooted in icicle, is actually a registered trademark of Unilever, so take care not to infringe that.
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.