Etymology

The term cnoidal was coined by Korteweg and de Vries in their paper in Philosophical Magazine (1895, series 5, vol 39, pp 422-443) to describe a class of solutions to the KdV equation which involve a Jacobi elliptic function. The Jacobi elliptic function involved is commonly written as , and the term cnoidal was designed to be analogous to sinusoidal, the word describing waves which involve the sine function.