Take the French word for god - dieu - and the Latin word for father - pater - and repeat them faster and faster.
Jupiter? By Jove, it is! But how (I hear you cavil) can that be? French didn't come till later. True, but then again you could do it with Zeus Pater. It all goes back to a Proto Indo European root: *dyeu-peter, meaning Godfather. That's why even over in India you got the Sanskrit Dyauspita, meaning god the father. In fact, the Romans got their Jupiter from Jove-Pater, which is why the father of the gods is often referred to simply as Jove.
People from Jupiter would be called Jovians, and they wouldn't be nearly as frightening as the martial Martians because they would be jovial.
Jovial originally meant pertaining to Jupiter and therefore mighty. However, if you're born under the planet Jupiter you grow up to be a happy chap, so jovial is an astrological term.