Priapus

Priapus was a minor fertility god in Greek mythology, who was also the protector of livestock, fruit plants, and male genitals. He was depicted as having an oversized and permanent erection. Sources differ as to who his parents were. Some say he was the son of the god Dionysus and the goddess Aphrodite; Dionysus and Chione; Hermes and Aphrodite; Zeus and Aphrodite; or Pan and Aphrodite. According to the myth, Hera cursed him while he was still in the womb of Aphrodite, because she was jealous that the Trojan prince Paris had picked Aphrodite as being the most beautiful of the goddesses and had given the Golden Apple of Eris to her. Hera's curse made Priapus impotent, ugly and foul-minded. The gods did not want Priapus to live with them on Olympus, and he was left on a hillside on Earth. There, he was taken by shepherds who raised him. Priapus later tried to rape the goddess Hestia, but was hit by a donkey, and this caused Priapus to lose his erection.
He also became the patron god of merchant sailing, protecting and guiding them through rough seas. It was common for merchants to carry a Priapus figure or a phallus on their ships as protection.