'Slave',from Latin 'Sclavus','Slav'-from the reduction to slavery of many Slavonic peoples of central Europe.Even the word slave derives from an ethnic,political perspective.

To add some Nietzschean meat to the bones,the following are statements from Nietzsche on Slavery;

"We must accept this cruel-sounding truth,that slavery is the essence of culture".

"Slavery is necessary in order to make the production of the world of art possible to a small number of Olympian men".

"War is just as necessary for the State as the slave is for society".[Nietzsche,'The Greek State',]

"Slavery enhances the species 'man' ".[Nietzsche,BGE 44]

All the above is clearly an ADVOCATION of slavery.Middle-class leisure lifestyle is just another form of slavery.Supermanhood is strenuous,dangerous and war-like.Modern work-shy hedonists are worse than their wage slave contemporaries.

The main philosophical desideratum for slavery is the need to create that widening of the soul,just as egalitarianism makes the soul narrow.Nietzsche explains;
"Without the PATHOS OF DISTANCE that grows from inveterate class differences,from the ruling caste's constant view downwards onto its underlings and tools,and from its equally constant practice in obeying and commanding,in holding down and holding at arm's length--without this pathos,that other,more mysterious pathos could never exist,that longing for ever greater distances within the soul itself,the development of ever higher,rare,more far-flung,extensive,spacious inner states,in short,the elevation of the type 'human being',the continual 'self-overcoming of the human',to use a moral formula in a supra-moral sense". [Nietzsche,BGE 257]

I think that makes matters crystal clear.