I never knew the source of that expression until just now: <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Turtles_all_the_way_down" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Turtles_all_the_way_down</a>