Etymology 

Bochart derives the word Blemmyes from two Hebrew terms, one a negation, the other meaning "brain", implying that the Blemmyes were people without brains.

Sources

Pliny the Elder writes of them that Blemmyes traduntur capita abesse, ore et oculis pectore adfixis ("It is said that the Blemmyes have no heads, and that their mouth and eyes are put in their chests"). Othello makes reference to them as "men with heads beneath their shoulders".

Origin of the myth

The Blemmyes were, in fact, a nomadic Nubian tribe described in Roman histories of the later empire. From the late third century on, along with another tribe, the Nobadae, they repeatedly fought the Romans.

Modern culture

In Umberto Eco's Baudolino, the protagonist meets Blemmyes along with Sciapods and a number of monsters from the medieval bestiary in his quest to find Prester John.