When people talk about “the whole nine yards,” just what are they talking about?

For decades the answer to that question has been the Bigfoot of word origins, chased around wild speculative corners by amateur word freaks, with exasperated lexicographers and debunkers of folk etymologies in hot pursuit.

Does the phrase derive from the length of ammunition belts in World War II aircraft? The contents of a standard concrete mixer? The amount of beer a British naval recruit was obligated to drink? Yardage in football? The length of fabric in a Scottish kilt (or sari, or kimono, or burial shroud)?

Type the phrase into Google and you’re likely to get any of these answers, usually backed by nothing more than vaguely remembered conversations with someone’s Great-Uncle Ed. But now two researchers using high-powered database search tools have delivered a confident “none of the above,” supported by a surprise twist:

Before we were going the whole nine yards, it turns out, we were only going six.

The recent discovery of several instances of “the whole six yards” in newspapers from the 1910s — four decades before the earliest known references to “the whole nine yards” — opens a new window onto “the most prominent etymological riddle of our time,” said Fred Shapiro, a librarian at Yale Law School who announced the findings in next month’s issue of The Yale Alumni Magazine.

Other language experts agree about the import of the discovery. “The phrase is interesting because it’s so mysterious,” said Ben Zimmer, the executive producer of Visual Thesaurus.com and Vocabulary.com, who has written previously on the search for its origin. “It’s been a kind of Holy Grail.”