Jupiter gets its name from the most powerful god in Roman mythology. The king of all other gods, Jupiter is the equivalent of Zeus in Greek mythology. It was the largest visible object in the night sky during the time of the Roman Empire, and thus named after its most important deity.
Jupiter has held many names and titles throughout history, though the most influential in modern times is that which originated from Roman mythology. Jupiter has been attributed with wine harvests and was hailed as the god of the sky, in addition to the god of thunder. In later times, the planet and deity were thought to influence the outcomes of battles, earning Jupiter a new title: the god of war.
Jupiter was the name under which oaths were taken and sacred offerings made, and was a symbol of the central authority of the Roman Empire. Ceremonial clothing and decorations for important political and religious events were often adorned with Jupiter's likeness.
Humans today know that Jupiter does live up to its name in many ways. It is the largest planet in the solar system and also protects Earth by deflecting and capturing comets and asteroids that would otherwise enter the inner solar system. The giant gas planet also helps to stabilize the orbits of the other planets, bringing a tenuous balance to the solar system as whole.