The phrase 'the whole nine yards' has a definitive historical origin, whether from ammunition belts, concrete mixer trucks, or ship masts.
Despite decades of etymology enthusiasts proposing explanations (WWII machine gun ammo belts were allegedly nine yards long, cement mixers hold nine cubic yards, etc.), no origin has ever been verified by linguistic research. The phrase appears in American English by the 1970s with no documented earlier usage, making it younger than most competing theories suggest. Linguists now classify this as an example of 'lost etymology', some phrases lack recoverable origins. All the colourful stories about nine yards are post-hoc inventions that feel plausible but lack documentary support. The phenomenon illustrates how humans hate semantic gaps and will happily invent false narratives rather than accept uncertainty.