From Wikipedia:
“Trochoid” is the word created by Gilles de Roberval for the curve described by a fixed point as a circle rolls along a straight line.
Trochoid is also a super cool iPhone app that is like a digital version of the spirograph. Neat, no?
To be fair, hypotrochoid is a more accurate word. Rather than a curve formed by circle rolling along a line, a hypotrochoid is “formed by a wheel rolling around the inside of a fixed circle.”
