Through Old French esclave (masculine and feminine), the noun slave is from Medieval Latin sclavus (feminine sclava).

This Latin noun is identical with the name Sclavus, meaning a Slav, the Slavic population in parts of central Europe having been reduced to a servile condition by the Germanic conquest. The Medieval Latin name corresponds to Late Greek Σκλάβος (= Sclabos).

These Latin and Greek names are renderings of a common Slavic self-designation with the base *slověn-, meaning a Slav.

Names derived from this base were also self-designations of particular Slavic peoples. For example, Slovene was used of the Slavs as a whole and also of the early East Slavic people living near Lake Ilmen, in northwestern Russia. The name Slovak is a parallel formation, with a different suffix, from the same Slavic base; it was originally the self-designation of a member of a Slavic people living in central Europe, particularly in the region of the western Carpathian Mountains.

The base *slověn- is perhaps a derivative of the Slavic root meaning word, speech. However, derivation from an unattested place name (in Old Russian, Slovutič′ was the Dnieper) is often considered more likely, since the cognates of the Slavic suffix *-ěn- in various Slavic languages occur almost exclusively in place-name derivatives.

In the sense of slave, German has retained the cluster scl- of the Medieval Latin name in Sklave (feminine Sklavin), while Slawe (feminine Slawin) means Slav.

In English, the reduction of scl- to sl- is normal, and the other Germanic languages show the following forms corresponding to slave: Dutch slaaf, Danish and Norwegian slave, Swedish slav.

But French (in esclave) and the other Romance languages have retained the cluster scl-:
– Spanish: esclavo (feminine esclava)
– Catalan: esclau (feminine esclava)
– Portuguese: escravo (feminine escrava)
– Italian: schiavo (feminine schiava)
– Romanian: sclav (feminine sclavă).

Although Romanian is essentially a Romance language, it also uses the Slavic word rob. For example, in Bulgarian, a Slavic language, роб (= rob) means slave and работа (= rabota), work.

In another Slavic language, Czech, robota means forced labour, drudgery. This is the origin of the word robot, denoting a machine resembling a human being and able to replicate certain human movements and functions automatically. This word was coined in the title of the play R.U.R.: Rossum’s Universal Robots (1920) by the Czech author Karel Čapek (1890-1938), who said that it was suggested to him by his brother Josef as an alternative to his original intention of coining a word ultimately from classical Latin labor. The original title of the play was in English, as though robot was an English word.

The classical Latin name for slave was servus, apparently from a root meaning heavy, burdensome, shared by:
– Latin serius, grave, serious, severus, serious, grave, severe,
– German schwer, heavy, difficult,
– Lithuanian svaras, weight, pound.

The Latin servus is the origin, via Old French, of English serf, designating an agricultural labourer bound by the feudal system who was tied to working on his lord’s estate.

From the noun servus, the Latin verb servire meant to be a slave, hence to serve, to be in service. Through Old French servir, it is the origin of English serve.

In German, from the sense (I am your) slave, servus is used as a greeting at meeting or parting, particularly in Bavaria and Austria. Some parts of Romania have adopted this German usage. This greeting is szervusz in Hungarian and serwus in Polish.

Similarly, the Italian greeting ciao is a dialectal alteration of schiavo and originally meant (I am your) slave.