A mondegreen is simply the mishearing or misinterpretation of a phrase in a way that gives it a new meaning. Sylvia Wright coined the term in 1954, writing that as a girl she had misheard the lyric “laid him on the green”
in the Scottish ballad “The Bonny Earl of Murray” as “Lady Mondegreen”. Most of my mondegreens are from song lyrics with my favorite being Creedence Clearwater Revival’s Bad Moon Rising that I still hear “There’s a bathroom on the right” with the correct line being “There’s a Bad Moon on the Rise”.
I believe that a lot of lyric misinterpretations come from mumbling singers, hard to hear sections of a song and accents of the lyricist. In the good ole days, you couldn’t just look up the correct lyrics in Google or even know a song title unless you happened to catch the DJ introducing the song.