I’ve always wondered why an equation with a squared variable was called a quadratic equation. Since ‘quad’ means four in Latin, shouldn’t a quadratic equation have cubed variables? Also consider quadrilateral and quadrant: both involve four elements. In case this has been keeping you up at night, Wikipedia has the answer!
The adjective quadratic comes from the Latin word quadratum for square. A term like x2 is called a square in algebra because it is the area of a square with side x. Quadratum is the Latin word for square because a square has four sides.
Whew! Now I can sleep at night.
If I only had paid more attention in my Latin class in Gymnasium (but that’s another story…)