Βέλγη

From LSJ

εἰς τετρημένον πίθον ἀντλεῖν → run water into a punctured pitcher, to the perforated jar bale water, labour in vain, labor in vain

Source

Spanish (DGE)

-ης, ἡ Belga ciudad quizá de la Galia Belga, Hsch.s.u. Βελγαῖος.