Apologies for the long title, which is almost a post in itself. I wish there were a word (and there probably is) for the linguistic category I want to discuss: those words that we use thinking we know what they mean only to find out, sometimes after many years and multiple degrees, that they mean something quite different. I am not referring here to malapropisms: comedic confusion of one, generally multisyllabic, word for another. Uttering a malapropism involves substituting one word for another with a similar sound, thereby generating a humorous and nonsensical sentence. I am also not talking about faux amis, those words in two languages that sound similar but have different meanings, such as embarrassed in English and embarazada in Spanish. No, what I have in mind is something more sinister: words that we trust, and that we have good reason to think mean what we think they mean, but that turn out not to be our friends at all.
For me, one such word was malinger. For years I thought that this word meant “serious and longlasting” in reference to an illness, when in fact it means, in the words of the OED, “To pretend or exaggerate illness in order to escape duty or work; to feign or produce physical or psychological symptoms to obtain financial compensation or other reward.”
Really, though, my supposition about malinger made sense. I had read it literally as a compound of mal and linger, and thus produced my definition. According to the OED, mal in malinger is probably the negative prefix derived from French and ultimately Latin, but in this case it is compounded with “heingre, haingre thin, emaciated.” Thus the meaning has nothing to do with lingering, although the form of the word probably is influenced by linger. None of this would have helped if I had ever solicitously said to a colleague or associate, “Oh dear, I’m so sorry to hear of your malingering illness.”
Had I been a Renaissance spelling reformer or an eighteenth-century grammarian, though, my mis-definition could have had much larger consequences. They didn’t always get their etymologies right either. Take island, for instance. Ever wondered why it has an s in it? Renaissance spelling reformers mistakenly thinking it descended ultimately from Latin insula, and so concerned about signaling this etymology that they stuck the s in. In fact island came from a perfectly good Old English word, igland (pronounced eelond), which was doing just fine without the s. (Such smug meddling has of course made spelling bees a lot more challenging).
I don’t remember if I have ever used the term malinger in speech or in writing; it’s not a term that comes up a lot (with either the correct or my erroneous definition). But finding out that you have been cherishing a word with the wrong meaning is a big shock (it’s okay, I’ve known for a while, and so I’m over the worst of it). Frankly it makes you wonder about all the others.