The Whole Nine Yards

A favourite among word-detectives precisely because the popular explanation is so confidently wrong. The most commonly repeated story claims it refers to the length of a machine-gun ammunition belt on a World War II fighter plane, so a pilot who'd "given the whole nine yards" had fired everything he had. It's a satisfying military image, and it's also impossible: the phrase is documented in print as early as 1907, decades before any WWII fighter existed, in an entirely non-military context. An earlier form, "the whole six yards," was already circulating in the rural American South by 1912. Despite enormous effort by professional etymologists, comparing theories about sailing-ship yards, cement-mixer capacity, and tailoring fabric lengths, nobody has found a version of the story that actually fits the timeline. The genuine origin remains unknown.