For an Italian word, ciao seems to belong to no one and to everyone all at once. It’s been adopted by as many as (or at least) 38 languages, and its influence extends well beyond Europe to Japan and Somalia. Throughout Latin America, people part ways warmly on the crest of this single syllable, and while not technically English, you’ll be widely understood (if not considered a tad affected) if you use it in the United States. Even if Italy lays claim to the origin of ciao, it has long since evolved into a cosmopolitan touchstone — a word that’ll register just about anywhere.

So what’s the deal with ciao? How did one small but mighty Italian word become a global gateway in and out of conversations with our closest friends? Spoiler: the origin of ciao is almost certainly not what you think it is, but its history makes an excellent case study for how languages evolve.

The Origin

Once upon a time, ciao was not ciao, but rather, s’ciao. This was an abbreviation of s’ciao vostro, which meant “I am your slave” in the Venetian dialect.

Venice was very active in the slave trade of the time, which means it’s impossible to entirely divorce this history from the word’s significations. However, its underlying meaning was somewhat more congenial than it sounds, and definitely a lot less, er, of the Britney Spears “I’m a Slave 4 U” persuasion. Essentially, to say s’ciao was to say “I’m at your service” or “I’m here for you if you need me,” and to express deep respect, loyalty, and trust. Supposedly, it was also used by everyone in spite of their social standing, and even among deeply devoted lovers.

Eventually, s’ciao became schiavo, the word that currently means “slave” in standard Italian. Its offshoot, ciao, mostly shed its servile connotations, but it didn’t become part of the official Italian language until the beginning of the 20th century. By this point, its usage had spread beyond the Venetian region into other parts of Northern Italy, and it had already begun showing up in the literature and songs of that era.

The Rest Was History

It didn’t take long for ciao to start catching on in other languages, but there’s no clear consensus on how, exactly, it was popularized.

One prevailing theory is that Ernest Hemingway introduced it to the English language in his 1929 novel A Farewell to Arms. Hemingway had been working for the Red Cross in the Venetian region during World War I, so he likely adopted some of the local lingo during his time there.

That doesn’t account for the considerable linguistic reach ciao has been able to achieve, however. It’s believed that Italian immigrants brought ciao with them when they settled in other parts of the globe, and it proved to be a rather infectious trend in their new home countries.

Visitors to Italy may have also been partially responsible for its spread. After World War II, Italy became a very popular vacation destination, and Italian culture and film became more widely consumed in other parts of the world.

When Should You Use Ciao In Italy?

Though the troublesome origin of ciao has very little to do with how it’s used as a loanword in other languages, Italians consider it a bit gauche when used in an inappropriate setting. This isn’t because it still sounds problematic necessarily, but because it can sound overly familiar in the wrong social situation. Imagine a stranger telling you “I am your servant” in English. If you listen carefully, you’ll notice that it’s actually not as universal of a greeting in Italy as one might think.

Ciao is generally used in only the most informal situations in Italian, and it’s much less commonly used among older generations. So really, you’ll probably only hear it being exchanged among close friends, within families, and amidst young people hanging out with their peers.

Though tourists and non-native speakers will generally get a pass if they use it in the wrong context, you’re better off opening with a buongiorno or salve if you’re talking to a waiter, an older relative, or someone you wouldn’t normally be on a first-name basis with.