This year marks a century since the song "Danny Boy" first weaved its way into Irish folklore. Its melody could be heard at President Kennedy’s funeral and it also played at the farewell to Elvis Presley.

The ballad that has proved irresistible to some of the biggest names in music is a song of love and loss - a lament for those missing home and each other.

“Danny Boy” arrived a century ago and never left. But arrived from where? Most people assume it’s from Ireland, but it’s not. It was written by an Englishman.

That Englishman was Fred Weatherly, a prolific songwriter - and later successful lawyer - who published 1,500 songs.

“One of the mysteries has always been is how this Englishman, who'd never been to Ireland, very upper crust, British, could write something that immediately took off for the Irish,” said Anthony Mann, Weatherly’s great-grandson. “Fred wrote so many songs that he never knew which one was going to be a go-er. It was like launching a series of pigeons really.”

Actually, at first “Danny Boy” didn't fly. The words were right but the tune was wrong, which is where Weatherly’s sister-in-law, Margaret Weatherly, comes in.

Margaret Weatherly was an Irish immigrant who sailed to America with Fred Weatherly’s brother in search of silver in Colorado. It was on a trip back to England in 1912 that Margaret Weatherly introduced Fred Weatherly to the ancient Irish melody, “The Londonderry Aire.”

Fred Weatherly fused that haunting melody with his heavy-hearted words and something magical happened. “Danny Boy” became a hit.

“He meant for it to be popular, he meant for it to be universal,” said music journalist Andrew Mueller. “There’s a very careful avoidance of specifics.”

Mueller told CBS News’ Charlie D’Agata that world events were about to lend the song a terrible resonance.

“One hesitates to call the first World War a stroke of luck, but I think for any work of art to endure it needs a stroke of luck and his lyrics for “Danny Boy” were published in 1913, a year before millions of people were finding themselves having to say goodbye to people who they hoped against hope that they might one day see again,” he said.

The theme of longing also struck a chord with many Irish emigrants who headed to America to escape the famine back home. Through the decades, the song became woven into the cultural fabric of the U.S. and beyond, often as a final farewell.

Elvis said he thought “Danny Boy” was written by angels and asked for it to be played at his funeral. At Princess Diana's church service, the words were different, but the haunting melody of “The Londonderry Aire,” the same.

And after the tragic events of Sept. 11, 2001, the strains of “Danny Boy” rose from the memorial services of so many Irish-American police and firefighters who were among the victims.

It's not just the notion of loss, but of someday being reunited, that's one of the reasons “Danny Boy” has never gone away.