"Spline" was a shipbuilder's flexible lofting strip for centuries before it named a mathematical curve

Long before it denoted a class of piecewise polynomials, a spline was a physical instrument of the shipyard. In naval lofting — laying out a hull at full scale on the mold-loft floor — a spline was a thin, flexible strip of wood or steel bent to pass through a set of fixed points and held in place by heavy weights called "ducks." The strip settled naturally into the smoothest ("fairest") curve consistent with those points, letting a draftsman draw fair hull lines by hand.

The mathematical object inherits this behavior almost literally: a spline curve is the one that minimizes bending energy while passing through its control points, exactly what a physical batten does. The craft tool supplied both the concept and the name. Isaac Schoenberg formalized the B-spline in 1946 (see claim-schoenberg-developed-splines-at-the-ballistic-research-lab-that-built-eniac), and the term later carried its shipbuilding origin, invisibly, into the automotive curve work at Renault and Citroën (claim-bezier-de-casteljau-independent-invention-secrecy-named-the-curve) and from there into CAD and digital typography.