The ballad our family traditionally sings at every funeral, Danny Boy, is a melody from an old Irish air "discovered" by a sister-in-law in the goldmines of Colorado [what was she doing in the mines?], Londonderry Air (AKA "Air from County Derry" or "Derry Air"), with words written by a London barrister and lyricist in 1910—a prime example of melodic borrowing.
Frederic Weatherly gave the ancient Irish tune, updated with his new lyrics to Elsie Griffin, who made it one of the most popular songs in the new century (first record was made in 1915). So we tend to think of him as the author and composer of Danny Boy. But he didn't compose the melody of the song, just the lyrics.
The story goes that the original air was collected from a blind fiddler by Jane Ross of Limavady in Northern Ireland, and published by musicologist and antiquarian, George Petrie in 1855, The Ancient Music of Ireland, by the Society for the Preservation and Publication of the Melodies of Ireland.
World famous song Danny Boy is taken from a melody composed by O’Cahan bard Rory Dall O’Cahan. The original version concerns the passing of the Chief Cooey-na-Gall whose death brought an end to a long line of O’Cahan chiefs in Northern Ireland. —Wiki
Folksingers have been swapping tunes and lyrics for eons—sometimes, in their travels, the bits get separated from each other—a muffled line becomes a mondegreen, oftentimes new songs arise from the ashes of the old.
Ye Highlands and ye Lowlands,So much for laying the poor old dead Earl of Moray down on the green. And what about Lady Mondegreen? She had some melons. A Cuban favorite: José can you see by the dawn's early light? Imagine a rainbow Hendrix: 'S'cuse me while I kiss this guy. Who knew that Kumbaya is really Come by Here—oh Lord.
Oh, where hae ye been?
They hae slain the Earl O' Moray
And Lady Mondegreen.
Our family simply slaughters the lyrics to Háva Nagíla at weddings. Gawd only know what we're boisterously singing while mangling the Grapevine. (Mondegreens in Hebrew are called watermelons.) Malachy McCourt thought The Hail Mary rosary phrase "amongst women" was "a monk swimming", which became the title of his book. Neil, who was an altar boy in Scotland, thought the Latin mea culpea was "Mexican cowboy." OK, so maybe he was stretching it a bit.