Bear with me on this, it does come back to words.

The mathematical equation whose graph is an ellipse is:
a * (x to the 2nd power) + b * (y to the 2nd power) = 1,
where a and b are any constants. a and be determine the size of the ellipse and how elongated it is. If a=b the result is a circle; thus a circle is a particular kind of an ellipse.

About 20 years ago a Dane, Piet Hein, experimented to see what kind of shape you'd get if you graphed a similar equation but change the 2's above. He found that if you change that number to about one-and-a-half, you get an esthetically pleasing shape, a compromise between an oval and a rectangle: one would roughly describe it as a rectangle with the corners cut off.

The term for that shape is "superellipse" Furniture in the Danish Modern style furniture often uses superellipses as, for example, the share of a tabletops. Danish traffic engineers design traffic ellipses in that shape, to minimize the sharp curves at the ends of the ellipse.

Hein has also authored numberous pithy poems, called "grooks".