How did the planet Jupiter get its name or what was it named after?

Many of Earth's Solar System's planets were named after Mythological gods and goddesses. Planet Jupiter is named after the Roman Mythological "head god", Jupiter. In Greek Mythology this same leader of the gods was called Zeus.

Prior to that, in Babylonian times, the planet was believed to have been their god Marduk.
Planet Jupiter was known long before many of our other planets were, because it is visible without the aid of telescopes in the evenings, and ancient civilizations could sometimes even see it during the day, when Earth was in a certain position.

The four moons of Jupiter were also named after Roman Mythological entities. All were named for Jupiter's lovers: Io, Europa, Ganymede, and Callisto.