An Etymological Dictionary of the German Language/Annotated/Zirkel
Zirkel, masculine, ‘circle, circuit, company, society,’ from Middle High German zirkel, Old High German zirkil, masculine, ‘circle,’ which is again derived from Latin circulus (Italian circolo, French cercle), ‘circle,’ Middle High German and Old High German zirc, ‘circle,’ from Latin circus (Italian circo).