"Epi oinopa ponton," a phrase used often in Homer's Odyssey, means “upon the wine-dark sea.” Mulligan’s attribution, “snotgreen,” casts a sarcastic light on this venerated epic coloring of the ocean. But Stephen recalls the phrase in Proteus and restores its Homeric tinge: "oinopa ponton, a winedark sea."
As the novel progresses, Stephen continues to brood on the phrase. In Wandering Rocks he looks through a jeweller's window at dust piled on "dull coils of bronze and silver, lozenges of cinnabar, on rubies, leprous and winedark stones." In Ithaca he sits across from Bloom and sees a Christ-figure "with winedark hair," the darkness perhaps speaking to the metaphysical darkness that he pondered in Nestor. In Cyclops, the Citizen too recalls this phrase as he pontificates about Irish trade in beer and wine with the Continent: "the winebark on the winedark waterway."
Epi oinopa ponton is one of many formulaic epithets that the Homeric bards used as easily remembered and metrically friendly crutches to fill spaces in lines. Singers in other archaic traditions of oral verse composition have practiced similar strategies to lessen the immense demands on their powers of improvisation and memory.