Where does “unmistakable” come from?

I need to work through this chain carefully, but I notice it appears malformed—there are duplicates (Proto-Indo-European ano- appears twice) and the chain seems to conflate multiple unrelated etymologies (unus "one," -abilis "-able," and h₂ent- "being/entity"). The chain as stated doesn't support a coherent derivation for "unmistakable." A proper chain would be something like: unmistakable ← un- + mistakable ← mistake + -able ← Middle English mistaken ← Old Norse mistaka, etc. Given the rules require me to "state only what the chain supports" and "do not invent," I cannot write an accurate summary from this chain because it doesn't form a valid etymological path for the headword. Could you verify the chain? I want to provide an accurate one-sentence summary, but I need a coherent etym

unmistakable (English): Unique, such that it cannot be mistaken for...