shamefaced: Showing modesty or shame.
This common word that has a fairly obvious meaning is, according to Merriam-Webster's Collegiate Dictionary, an example of an eggcorn that has established itself in the English language over the centuries.
First of all, an eggcorn, if you don't know, is the substitution of a word that sounds similar to the actual word in a well-worn phrase. The hallmark of a true eggcorn, though, is that the new "version" of the phrase makes a certain sense. For example, "for all intensive purposes," "a mute point," "mixmash," and of course "eggcorn." (For more info, check out the
Eggcorn Database.)
Good editors make sure that such eggcorns don't make it into print. But the Internet is rife with inexperienced writers publishing unedited (and largely unfiltered) text that includes bad grammar, misspellings, eggcorns, and all.
Because the Internet has turned everyone into "writers," we might be fooled into believing that eggcorns are a recent development. Not so, says my dictionary. According to M-W Collegiate Dictionary, Deluxe Edition, shamefaced comes from Old English scamfæst, or held fast by shame. A similar word, stedefæst, gives us the word steadfast. By all accounts, then, shamefaced should by shamefast.
According to the lexicographers, "Around the middle of the 16th century the alteration to shamefaced began to appear in print, and since then the folk etymology has been firmly established." (p. 1686) So well-established that most of us would do a double-take if we saw the word shamefast, which is acceptable.
To the wordies out there looking for a challenge: Can you find an eggcorn that predates shamefaced? (English only, please.)
Note that I am not arguing that we should stop saying and writing shamefaced. I firmly believe that etymology doesn't define a word, and it is a sorry argument for how a word should be used. Etymology tells you where a word comes from and not what it means, in the same way that one's family tree tells where a person came from but not who that person is.