I had to look this up, after reading #3 above
eggcorn (plural eggcorns)
(linguistics) An idiosyncratic but semantically motivated substitution of a word or phrase for a word or words that sound identical, or nearly so, at least in the dialect the speaker uses.
The subject of eggcorns was first introduced on the Internet on September 23, 2003 by Mark Liberman on the website Language Log.
He discussed the case of a woman who always thought the word acorn was egg corn. Later on, the word egg corn or eggcorn was suggested by Geoffrey K. Pullum to name such linguistic peculiarities.
Chris Potts has told me about a case in which a woman wrote "egg corns" for "acorns." This might be taken to be a folk etymology, like "Jerusalem" for "girasole" in "Jerusalem artichoke" (a kind of sunflower). But it might also be treated as something like a mondegreen (also here and here), the kind of "slip of the ear" that is especially common in learning songs and poems. Finally, it's also something like a malapropism, where a word is mistakenly substituted for one of similar sound shape.
deep-seeded instead of deep-seated
deformation of character instead of defamation of character
for all intensive purposes instead of for all intents and purposes
free reign instead of free rein
oldtimer's disease instead of Alzheimer's disease
on tender hooks instead of on tenterhooks
eggcorn - Wiktionary