“Huh” was unlike other question words in those languages—it was always one syllable, consisting of a short vowel sometimes preceded by a glottal consonant sound (one made deep in your throat). It also almost always had a rising pitch, the intonation most languages use for questions. “What,” by contrast, took a number of different phonetic and structural forms across the languages, like “que” in Spanish, or, gloriously, “wat,” in the Netherlands.

(Plos One)

The reason is that generally, we only say “huh” to signal to the other person in the conversation that we didn’t understand, and to get them to explain without being too obtrusive.

Ultimately, the authors ask whether “huh” is a universal word and decide on a “qualified yes”—though it doesn’t sound exactly the same everywhere, every language has a “huh,” and it’s almost always used for clarification (or “repair,” as it’s called in linguistic circles).

Here’s their theory as to why it happens: Languages may be specific to place, but conversations serve the same purpose everywhere. Our chatter works kind of like traffic: There’s a set of rules we’ve agreed to follow, and everyone generally tries to make the whole operation run smoothly. Someone asks a question, the other person answers. You try not to pause for too long between sentences. But the time between speakers is only about 200 milliseconds, so we often start preparing for our turn before the first person has finished talking. If we know we don’t understand or didn’t hear something, there’s an incentive to say something—“huh?”—as quickly and decisively as possible in order to get the other person to repeat themselves. No time to formulate an “excuse me?” or even a “pardon?”—this theoretical chat has places to be.

And because “huh” sounds so unlike the other words in most languages, it immediately captures the attention of the speaker.

"The reason you don't say something longer, like 'gagagaga,' is because then the other person might think you are trying to say something," Dingemanse told me. "But you don't have anything to say, so you say something very short."

The researchers also speculate that words like “oh,” “ah,” and “um” might be, like "huh," universal stoplights in our conversation flow, since iterations of those appear across languages, as well.

“The ultimate fit to the tight constraints of their conversational environments, these words stay put and help us conduct conversation in optimal ways,” the authors note.

For Dingemanse, the research shows that, "language has all these extremely important social roles. We use it for so many things more than conveying information."

What’s fascinating about this is that languages are otherwise so incredibly not similar. A recent widely circulated set of maps on European languages showed, for example, that “bear” is “medved” in the Czech Republic, and “bar” just across the border in Germany, and “ours” just one country further west, in France.

But “huh” seems to indicate that, around the world, we really all just want to interact as smoothly and clearly as possible. And also that life is full of tiny misunderstandings, no matter where you live.