The story
The idea of using such a circle to solve a quadratic equation is attributed to Thomas Carlyle (1795–1881).
Etymology from Wiktionary, CC BY-SA 4.0.
Carlyle circle
Today it means: A certain circle in a coordinate plane associated with a quadratic equation, having the property that the solutions of the equation are the horizontal coordinates of the intersections of the circle with the horizontal axis. Full definition →