This word demonstrates a phenomenon that everyone who uses language (especially English) should be interested it – because they are all interested in it; that is, they should take an interest in it, as they all have an interest in it. What I mean is that they should not be uninterested, as they are not disinterested.
OK, clearly, before I address the phenomenon, I need to address a matter of interest that might otherwise come between form and sense. It is, of course, the various related meanings of interest – the meanings that allow for the joke, “What’s the difference between a bank account and a politician? With a bank account, the more principal you have, the more interest you get; with a politician, the fewer principles you have, the more interest you get.”
Interest is, in the first place, something that pertains to a relationship. And by that, I don’t exactly mean the “OK, is there something between you two?” kind of relationship – except I do, too. It’s first of all a business relationship, indeed, and there is a legal claim between two parties or between a party and a property; there’s something between them – Latin inter, “between”, plus essere, “be”, makes interessere, a verb that became an English noun interess and from that an English verb interess, and those ended up morphing to interest (possibly from the past tense of the verb, interessed, but perhaps just from the epenthetic /t/ that sometimes shows up after a final /s/).
So if you have an interest in something, you have a share in it, something to gain or lose. If it gets you money, then you are gaining interest. From that comes the non-business sense we use when we say “Interesting!” And both are still used, but unquestionably the psychological sense is the more common.
And now we get to the interesting phenomenon. It has to do with a rule that guides commerce and also applies in vocabulary: in general, rarity increases valuation. Words that aren’t often used can tend to gain a certain added value from their rarity – a certain impressiveness factor. They also have a greater novelty effect. In short, they are like shiny, pricey little toys. These words are typically called low-frequency words by linguists.
Now, one possible effect of this is that such words get pressed into service to mean something that already has a word – a word that doesn’t mean exactly the same thing – just because they have a nice, ornamental effect. And who can be surprised? This is why people get shiny oak desks and brass nameplates, it’s why people buy expensive Swiss watches that can’t keep time as well as cheap quartz ones, it’s why people drive Ferraris on city streets, it’s what accounts for most of the annual revenues of Hammacher Schlemmer. Ayn Rand made a variety of mistakes in Atlas Shrugged, but one thing she pretty much got right was the part where the fantastic new alloy Rearden Metal, once made available for general use, is put to use for a wide variety of silly things that really don’t need it at all.
Oh, yes, sometimes people use their shiny new toys inappropriately. This is especially true in language. I find that unusual (foreign) punctuation marks and diacritics are especially often put to ornamental use. The umlaut is a favourite, as manifested in music – Blue Öyster Cult and Mötley Crüe being notable examples, and Spinal Tap (with an umlaut on the n which I can’t here reproduce due to character set limitations) parodying them – and elsewhere (a wine and art event in eastern Ontario calls itself ArteVïno, for instance).
Features of pronunciation are also subject to status-oriented fads. This is, for instance, how “r-dropping” came into New York and Boston English: it was at first a Britishism that was a mark of higher status; once it had been taken on by the lower classes, it was subject to becoming déclassé for the upper classes (moreso in New York than in Boston).
And, of course, words are subject to faddism of this sort too, and are at times pressed into service to mean things that are other from their established (dictionary) senses and that already have words that mean them. And here is where we get to the main point of interest.
If something holds no intellectual appeal for you, it is uninteresting, and you are uninterested in it. If you have no stake in something – you are in a position of impartiality to it; such financial holdings as you may have had have been divested, or such personal ties as you may have had have been released, or perhaps you never had any – you are disinterested. This is a nice distinction; it allows a person to be one and not the other, for instance (impartial but fascinated, or involved but uncaring).
Now, I will confess that disinterested has about as long a history of being used to mean “uninterested” as it has of being used to mean, well, “disinterested”, and uninterested was even at some past times occasionally used to mean “disinterested”, but over time the useful distinction has become well established, such that if a person sets out to learn the “proper” meanings of the words, the distinction is learned. But of course that’s not what always happens. Often people will see the word and make a guess at what it means.
And it just happens that “uninterested” – often itself no more than a long way to say “bored” – is a rather more common thing to speak of, and less nuanced, than “impartial due to lack of a stake in the matter”. It also just happens that disinterested is – or used to be; this is gradually changing due to the shift in use that I’m talking about here – a somewhat lower-frequency word than uninterested. It also is seen in more formal or technical or “important” contexts, and words are known by the company they keep. So it has come to be used for the same denotation as uninterested, but with the connotation “higher value” or “more impressive” or “more erudite” or similar: “I am disinterested” equals “This is uninteresting, and I’m smart.” (Always remember that when you say anything about anything, you are also saying something about yourself, about the context, and about the person or people you’re talking to through the way you choose to say it.)
Now, being a linguist, I am of course duty bound to be first of all a descriptivist, but being an editor and, after all, a user of English, I feel that I have not only a right but a duty to take an active interest in language usage, because, after all, I unavoidably have an active interest in it. And I like the use of disinterested to mean “free of any stake”; it’s a useful distinction. So I will continue to maintain and promote it, even in the face of what looks like an inevitable trend. But I will say this to thee: if thou usest disinterested as a synonym for uninterested, thou interrest the word in the crypt of redundancy, and thou interrest its sense in the crypt of meanings that no longer have words.
But now ’tis late, and I’m into resting. So I leave this in trust to you, and explicit est scriptum.