Half a century, it’s true, is not excessively long in the world of usage disputes. This is one of the mysteries of peevology: Why do certain innovations annoy people, year after year, while other changes pass unnoticed? Why are some terms “skunked,” in the coinage of usage maven Bryan Garner — trapped awkwardly between the traditional usage and the emerging sense — for decades? Why do others shift and adapt, almost unremarked, right under our noses?

As Liberman observed in a 2004 post at Language Log, “could care less” is not uniquely odd. Its pattern is familiar in other phrases like “I could give a damn” (and its ruder variants), and in the lyrics of Sammy Cahn’s 1940s classic, “I Should Care.” But whatever its sources — sarcasm, irony, Yiddish, or (as its detractors say) ignorance — “could care less” is snugly embedded in the American idiom. Yet the complaints keep rolling in.

But three decades on, “could care less” is flourishing. Ben Zimmer, examining its career last year in a column at the language website Visual Thesaurus, reported that “could care less” had steadily gained ground in edited prose. In American speech, according to research by linguist Mark Liberman, “could care less” is far ahead of the “couldn’t” version. And “could care less” is no recent corruption, Zimmer found; it shows up in print by 1955, only 11 years after the first sighting of “couldn’t care less.”

She couldn’t have known it at the time, but her reader’s trivial question would be wasting newspaper space (and bandwidth, too) for decades, as it blossomed into one of the great language peeves of our time. In 1972, Ann’s sister and fellow advice-peddler, Dear Abby, used “could care less” in print herself, and got an earful from readers. In 1975, the Harper’s usage dictionary declared that “could care less” was “an ignorant debasement of the language.” (Said panelist Isaac Asimov: “I don’t know people stupid enough to say this.”) In 1979, William Safire declared in his New York Times column that “could care less” had finally run its course: “Like most vogue phrases, it wore out its welcome.”

Ann voted with her reader — “the expression as I understand it is ‘I couldn’t care less’ ” — but she thought the question was trivial. “To be honest,” she concluded, “this is a waste of valuable newspaper space and I couldn’t care less.”

It was 50 years ago this month — Oct. 20, 1960 — that one of America’s favorite language disputes showed up in print, in the form of a letter to Ann Landers. A reader wanted Ann to settle a dispute with his girlfriend: “You know that common expression: ‘I couldn’t care less,’ ” he wrote. “Well, she says it’s ‘I COULD care less.’ ”

Among the peeves of 100 years ago, there are plenty of short-lived scandals, nits nobody has picked since the Treaty of Versailles. Usagists once scorned ovation (for “applause”) because the word “really” meant a minor Roman triumph. Dirt was supposed to mean “filth,” not good clean soil. Reliable was called a “monstrous” coinage, practitioner “a vulgar intruder.” But none of these rulings had much effect.

In our time, bemused has quietly shifted its sense from “befuddled” to something like “wryly or quizzically amused.” Apparently everyone finds it more useful in its new role, because objections (though they have been recorded) are relatively rare. The transition from “was graduated from college” (once the proper form) to “graduated from,” in the 19th century, met little resistance, and the 20th-century move to the simpler “graduated college” is well underway.

Other peeves just won’t die. Aggravate was aggravating Latin-minded usage writers in the 1860s, and you still hear from people who think it should mean only “make worse,” not “annoy.” Other issues nearing the 150-year mark are the propriety of “there’s two more,” the use of decimate to mean “destroy,” and the debate between “taller than I” and “taller than me.” Compared to these hardy perennials, “could care less” is a mere sprout.

But these days, we can circulate a lot more opinion in any given week. In its contentious half-century, “could care less” has probably generated as much usage comment as aggravate has in 150 years. And the volume isn’t slacking off: Last month in Reader’s Digest, this month in the Simmons College Voice, all over the Web, sober professionals and spelling-impaired amateurs continue to insist that “I could care less” really must mean “I care to some extent.” But it doesn’t; it never has; it never will.

Around the Internet, a popular saying (variously attributed) defines insanity as “doing the same thing over and over and expecting a different result.” After 50 years, it’s not likely that the next iteration of the argument against “could care less” will change American usage. So let’s stash the phrase in the “idioms” bin, along with “head over heels” and “have your cake and eat it too,” and forget about it. Truly, there is nothing more to say.

Jan Freeman’s e-mail address is mailtheword@gmail.com; she blogs about language at Throw Grammar from the Train (throwgrammarfromthetrain.blogspot.com).

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