Origin of the word ciao from Latin sclavus via a Venetian courtesy formula

"In Tuscany someone has begun to use the formula 'I am your slave'," wrote the Italian philologist Niccolò Tommaseo in the first half of the nineteenth century, while working on his Italian dictionary.

The universally known Italian greeting "ciao" derives from the Latin word sclavus, "servant, slave", in Italian schiavo. The word goes back to a handsome speech formula current in Venice, meaning something like our "Your humble servant".

From the eighteenth century it begins to be used in the abbreviated form s'ciao, "I am your slave", gradually coming into fashion and becoming common currency in the nineteenth century.

In time the word spread from Italy across the whole of Europe. Unlike the Italians, however, in Spain, Portugal, France, Romania and Russia people use "ciao" chiefly when parting, whereas in Italian it serves equally as a greeting and as a farewell.