This is an auspicious moment: a Language Log-ism has been entered into the Oxford English Dictionary. The latest quarterly update for the online revision of the OED includes this note:
As early as 1844, people were reinterpreting the word “acorn” as “eggcorn”, either deliberately, for humorous purposes, or in all innocence, in a struggle to analyse, in a way that made sense to them, what the word’s spelling must be: acorns are, after all, seeds which are somewhat egg-shaped, and in many dialects the formations acorn and eggcorn sound very similar. Since 2003, it has become a widely accepted term for this category of words as a whole, appearing in books and journals, and on the internet, often alongside its musical sibling, the mondegreen or misheard lyric (which first appeared in the OED in 2002). As such, it has now become an autological word: one which belongs to the category it describes.
Here is the 1844 citation for eggcorn as a folk-etymological spelling of acorn:
1844 S. G. MCMAHAN Let. 16 June in A. L. Hurtado John Sutter (2006) 130, I hope you are as harty as you ust to be and that you have plenty of egg corn [acorn] bread which I cann not get her[e] and I hope to help you eat some of it soon.
And here is the second definition, with the quotation paragraph showing off its Language Log pedigree:
2. An alteration of a word or phrase through the mishearing or reinterpretation of one or more of its elements as a similar-sounding word.
In allusion to sense 1, which is an example of such an alteration.2003 M. LIBERMAN Egg Corns: Folk Etymol., Malapropism, Mondegreen? (Update) in languagelog.ldc.upenn.edu (Weblog) 30 Sept. (O.E.D. Archive), Geoff Pullum suggests that if no suitable term already exists for cases like this, we should call them ‘egg corns’, in the metonymic tradition of ‘mondegreen’. 2004 Boston Globe (Nexis) 12 Dec. K5 Shakespeare's Hamlet said he was ‘to the manner born’, but the eggcorn ‘to the manor born’ has wide currency. 2006 New Scientist 26 Aug. 52/2 Eggcorns often involve replacing an unfamiliar or archaic word with a more common one, such as ‘old-timer's’ disease for Alzheimer's. 2010 K. DENHAM & A. LOBECK Linguistics for Everyone i. 13 Crucially, eggcorns make sense, often more than the original words.
There's already some grumbling about the wording of the definition. On the American Dialect Society listserv, Mark Peters points out "a gigantic omission":
The key element of an eggcorn is that it's a *logical* mistake–it has to make sense. That's what distinguishes it from a malapropism or mondegreen. When my mom calls carpal tunnel syndrome "carnal tunnel-vision syndrome," that's no eggcorn, because it makes no sense (it is awesome, though).
I agree with Mark: at least at Language Log Plaza and over at the Eggcorn Database, we've talked about eggcorns needing to "make sense in a new way" (even if that "sense" is a bit semantically tenuous). Mark does concede that "maybe 'reinterpretation' is supposed to cover the logic part," but it would be nice to have it a bit more spelled out.
Meanwhile, Neal Whitman muses:
For that matter, I have never found "eggcorn" to be satisfactorily distinguished from "folk etymology". Is a folk etymology an eggcorn that has become standard?
Eggcorns certainly don't need to be standard, or even on their way to standard. (The founding example, eggcorn, is, of course, resolutely non-standard.) Whether eggcorn carves out a meaningful territory distinct from folk etymology is open to debate, as it has been since that baptismal post in 2003. At the time, Mark Liberman wrote that the original example of egg( )corn "is not a folk etymology, because this is the usage of one person rather than an entire speech community." But folk etymology, construed broadly, can encompass this sort of idiosyncratic usage just as well as the more widespread alterations that lead to lasting diachronic change. For now, though, we won't quibble and instead will just bask in our lexicographical glory.
[Update: I neglected to mention that eggcorn is also in the latest edition of the New Oxford American Dictionary. The entry reads:
eggcorn n. a word or phrase that results from a mishearing or misinterpretation of another, an element of the original being substituted for one that sounds very similar or identical (e.g., tow the line instead of toe the line).
– ORIGIN early 21st cent.: with reference to a misinterpretation of acorn.
See a list of new NOAD words here.]