The Bézier curve was invented at two rival French carmakers — de Casteljau first — and Citroën's secrecy, not mathematical priority, decided whose name it got

The cubic curves that define PostScript and TrueType font outlines began as automotive body-design tools, developed in parallel at two competing French car companies. Paul de Casteljau solved the interpolation problem first, at Citroën: his method was documented at the French patent office INPI in 1959, months after he joined, and the intellectual property was registered with a bailiff in 1963 — but Citroën's confidentiality policy barred him from publishing, so the work stayed internal. Pierre Bézier developed his own curve formulation at Renault — aware of Citroën's courbes à pôles approach in broad outline via defectors from Citroën, but "not in possession of the precise theoretical background" (so the two constructions differ; the invention was parallel rather than fully independent) — and published it in 1966. Public credit defaulted to Bézier while de Casteljau's contribution stayed hidden: first mentioned in France in 1971, recognised internationally only from 1977, after Wolfgang Boehm found the work in 1975.

Verification (2026-07-12): Andreas Müller, "A tour d'horizon of de Casteljau's work," Computer Aided Geometric Design 113 (2024) 102366, open access (https://arxiv.org/abs/2408.13125), Tier 1–2 — "due to different corporate policies on communicating intellectual property, Bézier already gained internationally prominence in the late 1960's (Bézier, 1966, 1967, 1968); while de Casteljau was first mentioned in France in the 1970's … and was only recognised internationally from 1977 after being discovered by Boehm in 1975." On independence: Bézier "had knowledge of de Casteljau's courbes à pôles approach at large by some defectors from Citroën to Renault, yet he was not in possession of the precise theoretical background (Gardan, 2023). So Bézier came up with his own way of constructing those curves." De Casteljau's own retrospective account is de Faget de Casteljau, "My time at Citroën," CAGD 16 (1999) 583–586 (Tier 1; corroborates the internal, unpublished setting but carries no dates).

The naming that survives is a historical accident of corporate disclosure rather than of precedence: the curve carries Bézier's name, while the recursive evaluation procedure that draws it is universally called de Casteljau's algorithm. The priority ran the other way from the credit.

This is the mechanism-origin end of the same lineage traced in claim-spline-was-a-shipbuilders-lofting-tool-before-a-math-object and claim-schoenberg-developed-splines-at-the-ballistic-research-lab-that-built-eniac: curve-fitting math that moved from ship hulls through wartime artillery tables into car doors and finally into every digital font outline. It is also a clean case of credit assigned by institutional secrecy rather than merit, a pattern that recurs across the vault (compare claim-ann-hardy-tymshare-os-miscredited-to-husband).