The mondegreen is a phenomenon I discovered long before I learned its name, when I sang 'There is a land where southern skies / are gleaming with a thousand eyes' all the way through primary school before discovering my mistake.
A mondegreen, for anyone who doesn't already know this, is a creative mishearing of sung lyrics in which the brain, struggling to make sense of signals from the ear (in much the same way as it struggles to make sense of signals from the eye when you come out into the kitchen one morning to find there's water running down the walls because the hot water service has exploded: no no, says the brain, there must be a less expensive explanation), comes up with a mishearing that changes the original meaning but still makes at least a modicum of sense. Hence, instead of the correct but much duller 'thousand dyes', my apparently paranoid infant ear came up with 'southern skies are gleaming with a thousand eyes', an image that when I think of it even now, much less then, sends shivers up my spine.
But to the mondegreen. The traditional ballad The Bonnie Earl O'Murray contains the line 'They hae slain the Earl O'Murray and laid him on the green', misheard by the woman who coined the word as 'They hae slain the Earl Amurray and Lady Mondegreen.' Mondegreens usually rise from unfamiliarity with the words, concepts or syntax of the original, hence the best ones tend to come from children, particularly when struggling with the traditional language and stories of Christianity: the teddy called 'Gladly the cross-eyed bear', or that Christmas favourite, 'A Wayne in a Manger'.
Kids in particular tend to insert proper names, a way of making lyrics familiar by innocently inserting people they know: still on Christmas, we have 'Barney's the king of Israel' and 'Olive, the other reindeer', while in more patriotic mode there's 'José, can you see?'
The Wikipedia entry for 'Mondegreen' offers this meta-example:
'"It's hard to wreck a nice beach" ... originates in a story, perhaps apocryphal, about one of the earliest speech recognition programs being presented, at a demo, with someone saying "It's hard to recognize speech" and producing that phrase as the output. Regardless of the truth of the story, this mondegreen was used on a t-shirt given to Apple engineers who worked on the company's early speech-recognition software.'
And regardless of the truth of the mondegreen too, apparently. While 'It's hard to wreck a nice beach' makes perfect grammatical sense, it is obviously and demonstrably untrue: it is in fact fatally easy to wreck a nice beach. I've seen it done many times.
But when the erudite Tigtog left a comment a few posts back about eggcorns, and the equally erudite Laura posted a link to Language Log for further reference, I had no idea what either of them was talking about and had to go and investigate at once.
The eggcorn, it transpires, is a close relative of the mondegreen: again arising from unfamiliarity with, at least, the written version, an eggcorn is another sense-making operation in which you write down what you think you heard, aided (as with the mondegreen, and indeed with all folk etymology) by a kind of slippage of meaning in which the new version does make some kind of sense. An acorn is, after all, shaped sort of like an egg, and is, after all, a 'corn' or seed of an oak.
The difference between a mondegreen and an eggcorn is that the eggcorn does not depart from the original meaning, or at least not very far. I used to see a lot of eggcorns in my academic days: 'reigned in' for 'reined in' (both are to do with control) and 'honed in on' for 'homed in on' ('hone' being about sharpening things, including, presumably, focus) were the two most common.
My first encounter with someone else's eggcorn took place only a few metres from the Curramulka Primary School assembly site -- birthplace of the thousand gleaming eyes -- on the netball court, when a classmate insisted that the ball had gone out a bounce. Horrible pedantic infant that I was, I corrected her at once: 'Out of bounds,' I said schoolmarmishly. She stood her ground. She didn't know the word 'bounds' and as far as she was concerned the ball was out a bounce, because it had bounced out.
And for all I know, she's still saying it. I'm still singing 'summer skies are gleaming with a thousand eyes', after all.