Read this bit from Lewis Carroll's Alice's Adventures in Wonderland out loud:
"Tut, tut, child!" said the Duchess. "Everything's got a moral, if only you can find it."
Now read this aloud, from a 1931 issue of Popular Aviation:
"Tsk, tsk, Philip, why be ashamed of a perfectly good impression of a steam powered racer of the future."
Did your "Tut, tut" in the first one sound the same as your "tsk, tsk" in the second one?
No? Why not? They were meant to represent the same sound. You know, the sound you have probably made with the tip of your tongue many times just before saying "For heaven's sake!" (or something similar). The sound you make when a friend tells you about something boneheaded someone else did to them. The sound that has also been written by Walter Scott as "tchick" and by Rudyard Kipling as "tck." In phonetic terms, it's a velar-ingressive alveolar or pre-dental click (but if all you got out of that was "click," you still get the idea).
And yet, when we see it on the page, we tend to say "tut" to rhyme with "but" and "tsk" to rhyme with "risk" — which completely loses the connection to the original sound, even though it retains the attitude. But what are we supposed to do? We don't have any way to represent this sound in English spelling. It's not an English speech sound, and what "tut" and "tsk" represent is not a word.
But, as it turns out, that's exactly the point.
As Richard Ogden of the University of York puts it in a 2020 article, these clicks are "a way of audibly not saying something" — in other words, of "not producing talk when talk was due." We make these clicks to contribute to the interaction without committing ourselves in words to a position — or even, at times, to saying anything at all else at the moment: you can just make a "tsk!" and let the other person keep talking. Or, of course, you can add something like "Good grief!" or "That's really too bad" or any of several things that I'm not allowed to print here, at least not uncensored. The whole gamut, as Melissa Wright of Birmingham City University put it in a 2011 study, includes "irritation, sympathy, regret, disapproval, impatience, and exasperation."
Mark Dingemanse, of Radboud University in the Netherlands, explains in a 2020 article that these non-word sounds work well "precisely because they equivocate between sound and speech." In other words, as we might say, "I'm not saying ... but I'm not not saying ... " The more important thing they typically convey is the attitude towards the relationship with the other speaker in the conversation: alignment (as when expressing sympathy or echoing the other person's emotion) or disalignment (as when expressing disagreement with the other person's actions or attitude). And, as Ogden notes, they're often accompanied by other non-word gestures, such as winks or raised eyebrows — or, for disalignment, rolling the eyes.
Some speakers may use this click more than others, but, in general, everyone does it. It's standard among English speakers. Even though it's not a word in English, it's a not-word in English. Many other languages use it, too. (And, as you may know, in some languages, this sound is actually used in words – in Zulu and Xhosa, it's spelled c. In that context, of course, it doesn't have meaning of its own any more than any other consonant sound, such as "t" or "s.")
In fact, this click is only one of quite a few non-word sounds we regularly use as English speakers. Sighing loudly isn't saying anything, but it sure means something. We use whistles to convey attitudes clearly, too — think of how you might whistle when someone tells you that their neighbor's new car cost two million dollars, or that their prescription drugs add up to twenty thousand dollars monthly. And even sniffs can be used to communicate something.
But if you really want something to make you say "tsk," wait until I tell you that most of the time we use this sound, we actually don't use it to express any of the things that "tsk" and "tut" are supposed to express — irritation, sympathy, or the rest. According to Richard Ogden's analysis of collected real-world speech, more than half the time we click like this, it's to manage turn-taking in conversation. As Ogden says, it's a way of "not audibly saying something (yet)" — in other words, "I'm taking the floor now, and words are coming soon." This kind of click isn't always as pointed and emphatic as when we use it to convey something emotional, but it's the same basic sound. And it's still used in place of words — only in this case, it's serving as a temporary placeholder for words that are on the way.
But it doesn't just mean the same as "uh" or "um." It tends to signal a disjunction — a break, almost as though it's making a breaking sound. And, as Melissa Wright discovered, if you listen to a speaker's intonation after they make the click sound to signal that words are coming, it's often high and descending — like the intonation we typically use when saying "Aaaaaaanyway ... " There also tends to be a large inhalation between click and speech, another "Here it comes!" signal.
If you listen to people in casual conversation, you'll hear this kind of click every so often. You may even notice yourself doing it, though once you start watching, you can get self-conscious and uncertain. But keep an ear open, especially when someone wants to shift the topic or wrap things up. It's one of the things we do and respond to all the time, and yet seldom think about, precisely because it's a marker for something that's not there — yet.
Similar clicks are also used in the middle of conversation to buy time — as in when you're searching for a word, and you make several clicks in a row with the tip of your tongue — and even to match the speech rhythm of the other speaker while they're talking, almost like dancing along. But these kinds of clicks might be a little different-sounding — more like "t!" than "ts!" There are also the clicks you make with the side of your tongue, the "nudge nudge, wink wink" clicks — which are also the clicks some people use to tell a horse to start moving. But these are audibly different, and we're more like to put them on paper as something like "tchick, tchick."
But when we put any of these not-words down on paper, they become words. We start moving them around in sentences, and we start pronouncing them according to how we spelled them. When we make a word of the alveolar click — whether it's "tut" since before Shakespeare's time, or "tsk" since about a century ago (yes, it really is that recent!) — it's like a mermaid that takes human form: It loses its magic. You commit to a certain meaning, and yet not exactly the meaning you were not-not-saying before. It's almost ironic, or at least playful, like saying "meow" rather than actually meowing.
I guess the moral of this story, if we can find one, is that you can say a lot without saying something, but it's not the same as what you can say if you do say something. Or something like that. Tsk.