Where does “hydrocyanic” come from?

I need to work through this chain carefully, but I notice there are significant issues with the provided etymology chain. The chain as given shows: - English cyanic - English cyan - Ancient Greek ὕδωρ (hydōr, "water") - Latin -icus - Proto-Indo-European -kos (repeated three times) This chain doesn't make coherent sense. "Hydrocyanic" should derive from "hydro-" (from Ancient Greek ὕδωρ, "water") + "cyanic" (from "cyan," which comes from Ancient Greek κύανος kyanos, "dark blue"). The chain provided is missing κύανος and has structural problems. However, following the instruction to "state only what the chain supports" and not invent steps, I cannot construct an accurate etymology sentence from this chain as presented, because the chain itself appears corrupted or

hydrocyanic (English): Of or pertaining to hydrocyanic acid or its...