Diodorus Siculus provides the first appearance of the Omphale theme in literature, though Aeschylus was aware of the episode. The Greeks did not recognize her as a goddess: the undisputed etymological connection with omphalos, the world-navel, has never been made clear. In her best-known myth, she is the mistress of the hero Heracles during a year of required servitude, a scenario that offered writers and artists opportunities to explore gender roles and erotic themes.