[This entry is taken from a chapter of Part II of the open-source textbook Spanish-English Cognates: An Unconventional Introduction to Spanish Linguistics.]
Eng. ciao ~ Sp. chao/chau
One of the most curious facts about the cognates Eng. slave ~ Sp. esclavo is that they are cognate with the common Italian and now also international salutation ciao. In the original Italian, this word is spelled ciao and pronounced [ˈʧa.o]. In English, the spelling is also ciao and the pronunciation [ˈʧaʊ̯], with the diphthong [aʊ̯], as in cow and mouse. In Spanish, it can be pronounced [ˈʧao̯], with an atypical diphthong [ao̯] (traditionally known as a sinéresis, cf. Part I, Chapter 7), but many convert it to the more common diphthong [au̯], resulting in the pronunciation [ˈʧau̯]. Spanish has regularized this word’s spelling to be written following Spanish orthography, according to which the sound [ʧ] is written 〈ch〉 (and only 〈ch〉, unlike in English). Just like there are two possible pronunciations, [ˈʧao̯] and [ˈʧau̯], the word can also be spelled either chao, which is more common in Spain, or chau, which is more common in Spanish America.
In English and Spanish this word is mostly used with the meaning ‘goodbye’, but in the original Italian language, it is a general-purpose salutation which can mean ‘hello’ as well as ‘goodbye’. Such multi-purpose salutations are common in many languages, e.g. Hebrew shalom, Arabic salaam, Hawaiian aloha, and Northern Basque agur. In other words, Italian ciao can mean ‘hello’, equivalent to (formal) salve and buongiorno, or ‘goodbye’, equivalent to formal arrivederla, arrivederci, or colloquial ci vediamo.
The word ciao with the form and meaning that we are discussing originated in the Venetian Romance language, known as Venetian or Venetan (Sp. idioma veneciano or véneto). Since the unification of Italy in 1871 (after a period of wars of Italian unification or Risorgimento ‘Resurgence’ in 1848-1871) and the adoption of a standard Italian language based on the Tuscan Romance variety, the Venetian Romance variety has been popularly considered to be a dialect of Italian, even by its speakers. From a linguistic and historical perspective, however, this Romance variety can be seen as a separate language, one with several varieties of its own (cf. Part I, Chapter 3).[i]
In Venetian, the word for ‘slave’ is and was sciàvo, typically pronounced [ˈsʧao], which is a cognate of the words Eng. slave and Sp. esclavo, since it also descends from the same Medieval Latin word slavus. This word came to be used colloquially in a perfunctory manner in Venetian as a salutation, no doubt with a polite self-deprecating sense ‘(I am your) slave/servant’. The word’s form also got reduced from sciàvo to sciao and eventually, ciao.
This use of a self-deprecating expression is somewhat analogous to the way that English uses similar expressions in not too different contexts, such as the expressions at your service or your obedient servant, the latter used in correspondence in not too distant times. Equivalent expressions in traditional Spanish include ¡servidor de usted! ‘your servant’ (DCEH), ¡a su servicio! ‘at your service’, and, in writing, su seguro servidor ‘your humble servant’ (used to refer to oneself), all expressions that sound archaic today. But even today, in Spain, when one reaches a line and asks who the last one is (¿quién es el último?), it is possible to hear a (typically older) person answer ¡servidor(a)!
Note that there is a precedent for the use for a word meaning ‘slave’ in Europe as a greeting. We are referring to the original word for ‘slave’ in Classical Latin, namely sĕrvus. As we will see below, in some central European languages or language varieties, such as Southern German, Hungarian and Polish, descendants of this Latin word have also come to be used as a greeting, much like ciao is used now in Italian, English and Spanish.
As we said, eventually this Venetian greeting was shortened to ciao and the original connection to slavery or connotations about humbling oneself were completely lost. By the turn of the 20th century, Venetian ciao had been adopted in Northern Italy and eventually in all of Italy and from there, it spread to many other countries all over the world, becoming a truly international greeting. The greeting is not all that common in Spain, but it is very common in many countries of Spanish America, especially in South America. (Remember that many Italians emigrated to South America in the 19th and 20th centuries.) In the English-speaking world too, the greeting is more common in some countries than others. Thus, for instance, it is more common in Australia and South Africa than in the United States. It is said that the word ciao was popularized in English in Hemingway’s 1929 book A Farewell to Arms, a book about northeast Italy during World War I.
As we said, this word has become truly international in the last one hundred years. Among the many versions of this word in different languages, we find the following (they all mean ‘goodbye’ unless otherwise mentioned): Catalan ciao or txao, French ciao or tchao, German ciao or tschau (in Switzerland, it also means ‘hello’), Greek τσάο (tsao), Hebrew צ'או (chao), Japanese チャオ (chao) ‘hello’ or チャオチャオ (chao chao) ‘bye bye’, Portuguese tchau, tchau tchau or (diminutive) tchauzinho, and Russian ча́о (čáo).[ii]