Where does “treadmill” come from?

I need to work through this chain carefully, but I notice there are some issues with the etymology chain provided. It appears to have repetitions and doesn't clearly connect to "treadmill" in a coherent way. The chain shows: English mill | Latin millesimum | Middle English -en (repeated) | Proto-Indo-European dreu- (repeated) | Proto-Indo-European en This doesn't form a logical etymology for "treadmill." A treadmill is a compound of "tread" + "mill," but the chain provided seems to only address "mill" and doesn't explain how these elements combine or derive properly. Given the constraint that I must "state only what the chain supports" and "do not invent," I cannot construct a single coherent sentence that accurately represents this chain as written, because the chain itself appears incomplete or corrupted for the headword "treadmill." Could you verify the etymology

treadmill (English): A piece of indoor sporting equipment used to...