This mosaic is located in the House of the Menander in Pompeii at the entrance to the caldarium, the hot bath. The house taked its name from a painting believed to be of the fourth century BC Greek playwright Menander, located in a niche in the peristyle (colonnaded open court) of the house. Both the floors and the walls of the house were decorated in the Second Pompeiian Style and were likely constructed toward 20 BC. It is genberally accepted that the entire bath floor of the building was created by one master at one time. In having a private bath complex installed -- one of three such private baths in all Pompeii -- the owner advertised his wealth and status.
The mosaic depicts a black slave carrying oil bottles (askoi) into the bath complex. Both slave and bottles were commonplace in baths. Like the Priapus fresco also featured elsewere in this exhibit, the slave is a comedic figure with his large penis representing over-indulgence. However, his placement in the bath is no accident. Humor and the laughter which accompanied it were believed to avert the "evil eye", to which one was especially vulnerable while exposed and naked in the bath. The Romans believed that when someone looked at you enviously, you were exposed to harmful particles emitted from their eyes.
The colour of the slave, arguably and Ethiopian -- this people was held by the Romans to be sun-darkened -- may have served as a warning to batheres that they were about to enter a hot bath. Bare-footed bather may have been thankful for this warning.
Though the slave's large penis draws attention to his sexulaity, his image was perhaps more apotropaic than simply sexual. He is an example of how protection from the supernatural could be one of the functions of sexual depiction.