Differential geometry
Non-Euclidean and Riemannian geometry: the mathematics of curved space.
Founded: 1854 — Riemann's habilitation lecture on the geometry of curved manifolds
The claim
Carl Friedrich Gauss, 1829: “It may take very long before I make public my investigations on this issue… for I fear the clamor of the Boeotians.”
Source: Letter to Bessel, 1829.
A different failure mode from Hardy's or Kelvin's: Gauss valued this mathematics highly and wasn't calling it useless — he feared hostile reception from unsympathetic contemporaries (“Boeotians,” a classical slur for the intellectually dull), not that the work lacked value. The field was nonetheless widely regarded as a logical exercise with no physical relevance until the 1860s–70s.
What happened
General Relativity (1915) — Einstein. Requires Riemann's geometry of curved manifolds as its literal language.
GPS (1977) — Uncorrected relativistic clock drift ⇒ roughly 10km/day position error — confirmed on the NTS-2 satellite.
61 years — founding (1854) to General Relativity (1915)
Verdict: Named dismissal, later applied.
Confidence: high.