It's still an unraveling mystery.

For months, the yellow ribbon has been splashed across the landscape as a symbol of the hostages -- their captivity and their elusive freedom.

How the ribbon originally became a symbol of freedom or homecoming is unclear, however.

In the early 1970s, a couple of songwriters' pulled the symbol of a yellow ribbon out of the air because they thought it was "musical and romantic." And, anyway, they figured nobody would buy a song about a white kerchief wrapped around some old tree. So their song tied a yellow ribbon round a tree as a homecoming welcome for a returning prisoner.

But now that their creation, "Tie a Yellow Ribbon 'Round the Old Oak Tree" is a national symbol, historians, archivists and the curious are trying to solve the yellow ribbon, mystery. "Just where did all this ribbon business begin?" they were asking yesterday.

Some traced it to a 1969 book of lectures -- only there the returning prisoner was greeted by an old apple tree decked out with white ribbons.

Others traced it to the 1949 John Wayne movie, "She Wore a Yellow Ribbon," a cavalry saga about the Old West after Custer's Last Stand. In that one the lyrics went:

"Round her neck she wore a yellow ribbon. . . She said 'It's for my lover who is far, far away." Previous versions of that song date back as far as 1838.

And although many of those who started the ribbon mania have said it dates to an old Civil War custom when women greeted their soldiers with these ribbons, noted Civil War historians said yesterday they have heard of no such thing.

"I don't recall anything like that," said historian and author Shelby Foote."But yellow was the color that the cavalry wore on their uniforms. It shows the arm of service and goes all the way to the Revolution."

One thing is clear. The story of a returning prisoner asking for some sign that he is wanted at home and getting it in the form of a beribboned tree goes far back into folklore. New York attorney Peter Herbert, who defended a copyright suit against the "Tie a Yellow Ribbon" writers, traced the story to a Mormon publication that told of a returning convict who was greeted by a tree ablaze with ribbons of every color -- including, of course, yellow.

Library of Congress archivist Jerry Parsons said yesterday that it was once customary for loved ones to greet returning soldiers by tying pieces of white rags to trees.

This certainly hasn't stopped the yellow ribbon explosion around the nation that began when Penne Laingen, wife of hostage Bruce Laingen, tied one around a tree in the front yard of her Bethesda home. And it certainly hasn't deterred Vietnam veteran Jason French, who founded the National Yellow Ribbon Campaign last July and has traveled the country buying $32,000 worth of ribbon that would span 600 miles.