The term "eggcorns" originated with a misinterpretation for “acorn". It covers linguistic mistakes that have no other clear term. Eggcorns was eventually adopted as the official term for misheard words that one person may unintentionally distort while trying to figure out what they are. It is generally confined to one individual, and may become a trademark of sorts with that person.
Eggcorns are not considered mondegreens, which are phenomena that apply to something heard like song lyrics or performances. One of the most well-known is a misheard phrase from American guitarist Jimi Hendrix’s 1967 song “Purple Haze.” Quite a few people have mistakenly heard “Excuse me while I kiss the sky” as “Excuse me while I kiss this guy.” A search on the Internet will find hundreds of amusing examples of mondegreens from various songs, poems, and plays. The term mondegreen was coined in a 1954 essay by author Sylvia Wright, who as a child misheard a name in a Scottish ballad as “Lady Mondegreen”.
Nor are eggcorns quite malapropisms, which occur when the speaker or writer misuses a similar-sounding word in an exaggerated fashion. The term comes from the French mal á propos, which means “inappropriate.” Examples of malapropisms would be “The father was some sort of civil serpent,” or “A rolling stone gathers no moths.” In the US, they are sometimes called "Bushisms" after former President George W. Bush, who was quite famous for them. A British expression, Colemanballs, pokes fun at BBC announcer David Coleman, who also had a habit of inserting malapropisms in his speech.
Eggcorns differ from both mondegreens and malapropisms. They are considered a phonetic mispronunciation of a particular word in an attempt to make an intelligent guess at what that word actually is. The mind simply makes a linguistic substitution. Eggcorns usually originate and are attached to one person rather than a group of speakers. They sometimes find their way into the vernacular, especially with the advent of the Internet, where amusing mistakes can spread widely.
Famous eggcorns include “duck tape,” mispronounced from “duct tape,” a fibrous adhesive product used on heating and air conditioning ducts. This particular error is now actually a brand name. Another is “old-timer’s disease,” referring to Alzheimer’s disease. Since the condition often strikes older adults, it is easy to see the thought process in the creation of this eggcorn.