One name for the figure used by Euclid to prove the Pythagorean theorem.
Windmill
See also
Bride's Chair, Peacock Tail, Windmill GraphExplore with Wolfram|Alpha
Cite this as:
Weisstein, Eric W. "Windmill." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/Windmill.html