I remember that when I took my Numerical Analysis class, the professor said the spline interpolation take its name from a kind of wood sticks used to draw curved lines. Also Wikipedia say that the name is due to those elastic rulers:
Elastic rulers that were bent to pass through a number of predefined points (the "knots") were used for making technical drawings for shipbuilding and construction by hand
I now wonder if the spline are only inspired to those rulers or if they moreover precisely follow the physical laws that govern the bending of particular wood sticks (and if it is not the case, I ask if anyone know of any alternative physical interpretation of them).