"Ay, it's a whole mystery."
Those who study the origins of words have always been intrigued by the statement "the whole nine yards", which means "completely" or "everything".
Nobody knows exactly where the phrase came from:
Popular theories about the origin of the phrase, often espoused with great conviction, include the amount of cloth in a Scottish kilt, the capacity of a concrete truck, and, especially, the length of certain World War II military equipment, usually aircraft machine gun ammunition belts. But every theory must be assessed in light of the dated documentation—or lack thereof.Word sleuths traced it back to 1957, but before that the trail grew cold. Then, strangely enough, a reference was found further back in time, in 1912. But it wasn't for the exact phrase "the whole nine yards". Instead, it was for a different phrase, almost exactly the same, that does mean the same thing: "the whole six yards."
Somehow, over time, an extra three yards was added to the phrase. Why did that happen? That's still a mystery.
Read more: You can quote them. The inflation of “cloud seven” and “the whole six yards.” Yale Alumni Magazine>>
Of course, it could also have its origins in a bawdy song. (This one is by Lolly Foy):
Well, Angus was a happy lad, for soon he would be wed.
He'd found a brisk and bonnie lass to take him to his bed.
And happier still his mother was that he had found a wife,
For, truth be told, she'd often feared she'd be stuck with him for life.
Chorus: It's a fine thing, a bonnie thing, the grandest ever seen.
(Repeat last line of verse)
In honor of the grand affair that wedding day would be,
She set about to weave a kilt, the finest ever seen.
The night before the wedding, when the kilt was finally done,
She called young Angus over and she tried it on her son.
She wound the kilt about him and she wound, and wound, and wound,
And when she finished winding, it was still eight yards too long.
"Never fear, my bonnie boy. We'll simply cut it off,
And to your blushin' bride we'll give the extra length of cloth."
Now Angus was so pleased, y'know, his heart had swelled with pride.
He felt that he must rush right out and show it to his bride.
'Twas raining, so he grabbed a cloak to shield him on the moor,
But in his haste to be away his kilt slammed in the door.
Well, Angus was in such a rush to show off for his bride,
He never really noticed that he had left his kilt behind.
He knocked upon her door and cried, "Oh, let me in, I pray!
I've something that you've got to see before our wedding day."
Now, Bridget let him in, y'know, but said, "Ye cannot stay.
For I've got to have my beauty sleep before our wedding day."
"I'll only be a moment, love, but it's so grand, my dear,
Ye've really got to see what I'm a-hiding under here."
Now, when the cloak was thrown aside and Angus stood quite bare,
We must admit she was impressed and tried hard not to stare.
"Oh, love, I'll ne'er see finer, though far and far I roam!"
"Well, lass," he cried, "that's nothing! I've got eight more yards at home!"
- Angus and the Kilt, The Mudcat Cafe>>
- The Whole Nine Yards, Snopes>>