Yes, I did know that the word trundle made sense, because I have come across it before in books, as a kid, in stories for children. E.g. "The gardener trundled

Yes, I did know that the word trundle made sense, because I have come across it before in books, as a kid, in stories for children. E.g. "The gardener trundled his wheelbarrow along the (garden) path." (The word is not use much nowadays; archaic, as the dictionary entry says.) I was only speculating about the connection between the two words (trundle and treadmill), because they sound vaguely similar. Maybe they have a common Latin or Old English or Old German root, as many English words do. Update: I checked, and it seems I may have been partly / loosely correct about the etymological connection: https://www.merriam-webster.com/dictionary/trundle https://www.merriam-webster.com/dictionary/trundle Etymology Noun and Verb from trundle small wheel, alteration of earlier trendle, from Middle English, circle, ring, wheel, from Old English trendel; akin to Old English trendan to revolve https://www.merriam-webster.com/dictionary/treadmill https://www.merriam-webster.com/dictionary/treadmill c : a mill worked by persons treading on steps on the periphery of a wide wheel having a horizontal axis https://www.merriam-webster.com/dictionary/tread https://www.merriam-webster.com/dictionary/tread tread 2 of 2 noun 1 a(1) : the part of a wheel or tire that makes contact with a road or rail Italics mine.