A recently-coined word to describe a certain kind of linguistic mistake
, of which the classic example, for which it's named, is calling an acorn
an egg corn
It was discussed by Mark Liberman in the blog Language Log1 on 23rd September 2003. The woman who had written egg corns apparently spoke a dialect in which it was an exact homophone for acorns. The question arises as to what exactly this phenomenon is.
It's not just a spelling mistake. Something more had gone on: a reanalysis into new segments. So it's something like a folk etymology, a popular explanation of a word's meaning by confusing it with similar-sounding words that would make sense as a meaning. But it was only one person's doing it, and the "explanation" of acorn as egg corn doesn't really make sense.
When one person just makes a mistake about a word, that's called a malapropism, after the comic character Mrs Malaprop in Sheridan; but she confused words that had nothing much in common except a large proportion of their sounds: allegory and alligator, for example. If the egg corn woman had a dialect in which that was an exact match for acorn, then it isn't a malapropism.
A mondegreen is a somewhat similar thing: when you mishear a song lyric. The word comes from an old ballad, when someone (in the 1950s) wrote that she had heard "Lady Mondegreen" in the words, when in fact they were "laid him on the green". But mondegreens come about because singing degrades phonetics a bit: we often can't properly hear the words. So again, not quite right for acorn/eggcorn.
Mark Liberman's fellow blogger in Language Log, Geoffrey Pullum, suggested that of course it should be called an eggcorn, and this name seems to have stuck, and is spreading in the language community. They have recorded a number more, including:
ad itch, for adage
wedding vowels, for wedding vows
shoe-in, for shoo-in
hone in on, for home in on (possibly)
reigns of power, for reins of power
Note that some of these occur quite a few times if you google for them, and do make a degree of sense, so they're starting to look like folk etymologies.