From Word.com, the newsletter for subscribers on Merriam-Webster:
The word comes from a story told on herself by writer Sylvia Wright, in an article published in Harper's Magazine in November 1954. When she was a girl, wrote Wright, her mother sang her the ballad The Bonny Earl of Moray. One verse goes like this:
O where hae ye been?
They hae slain the Earl of Moray
And hae laid him on the green.
Young Sylvia heard the last two lines this way:
They hae slain the Earl Amurray And Lady Mondegreen.
After learning she mourned in vain for poor Lady Mondegreen, Wright's chagrin changed into amusement and inspired the neologism. Mondegreen has since caught on.
Here are some great Rock and Roll mondegreens:
Wrong lyric: The ants are my friend, they’re blowin’ in the wind
Right lyric: The answer, my friend, is blowin’ in the wind
Creedence Clearwater Revival, “Bad Moon Rising”
Wrong lyric: There’s a bathroom on the right
Right lyric: There’s a bad moon on the rise
The Rolling Stones, “Paint It, Black”
Wrong lyric: I see a Renoir and I want to paint it black
Right lyric: I see a red door and I want to paint it black
Me? I always love learning what kids hear/say when singing the national anthem or the Pledge of Allegiance.